Refactor agent architecture and add session storage

Major architectural improvements:
- Renamed AgentSession → Agent (state/ → agent/)
- Removed id field from AgentState
- Fixed transport abstraction to pass messages directly instead of using callbacks
- Eliminated circular dependencies in transport creation

Transport changes:
- Changed signature: run(messages, userMessage, config, signal)
- Removed getMessages callback from ProviderTransport and AppTransport
- Transports now filter attachments internally

Session storage:
- Added SessionRepository with IndexedDB backend
- Auto-save sessions after first exchange
- Auto-generate titles from first user message
- Session list dialog with search and delete
- Persistent storage permission dialog
- Browser extension now auto-loads last session

UI improvements:
- ChatPanel creates single AgentInterface instance in setAgent()
- Added drag & drop file upload to MessageEditor
- Fixed artifacts panel auto-opening on session load
- Added "Drop files here" i18n strings
- Changed "Continue Without Saving" → "Continue Anyway"

Web example:
- Complete rewrite of main.ts with clean architecture
- Added check script to package.json
- Session management with URL state
- Editable session titles

Browser extension:
- Added full session storage support
- History and new session buttons
- Auto-load most recent session on open
- Session titles in header

packages/web-ui/src/dialogs/ApiKeyPromptDialog.ts

@@ -64,11 +64,8 @@ export class ApiKeyPromptDialog extends DialogBase {
 				children: html`
 					${DialogHeader({
 						title: i18n("API Key Required"),
-						description: i18n("Enter your API key for {provider}").replace("{provider}", this.provider),
 					})}
-					<div class="mt-4">
-						<provider-key-input .provider=${this.provider}></provider-key-input>
-					</div>
+					<provider-key-input .provider=${this.provider}></provider-key-input>
 				`,
 			})}
 		`;

packages/web-ui/src/dialogs/PersistentStorageDialog.ts

@@ -0,0 +1,141 @@
+import { Button, DialogBase, DialogContent, DialogHeader, html } from "@mariozechner/mini-lit";
+import { customElement, state } from "lit/decorators.js";
+import { i18n } from "../utils/i18n.js";
+
+@customElement("persistent-storage-dialog")
+export class PersistentStorageDialog extends DialogBase {
+	@state() private requesting = false;
+
+	private resolvePromise?: (userApproved: boolean) => void;
+
+	protected modalWidth = "min(500px, 90vw)";
+	protected modalHeight = "auto";
+
+	/**
+	 * Request persistent storage permission.
+	 * Returns true if browser granted persistent storage, false otherwise.
+	 */
+	static async request(): Promise<boolean> {
+		// Check if already persisted
+		if (navigator.storage?.persisted) {
+			const alreadyPersisted = await navigator.storage.persisted();
+			if (alreadyPersisted) {
+				console.log("✓ Persistent storage already granted");
+				return true;
+			}
+		}
+
+		// Show dialog and wait for user response
+		const dialog = new PersistentStorageDialog();
+		dialog.open();
+
+		const userApproved = await new Promise<boolean>((resolve) => {
+			dialog.resolvePromise = resolve;
+		});
+
+		if (!userApproved) {
+			console.warn("⚠ User declined persistent storage - sessions may be lost");
+			return false;
+		}
+
+		// User approved, request from browser
+		if (!navigator.storage?.persist) {
+			console.warn("⚠ Persistent storage API not available");
+			return false;
+		}
+
+		try {
+			const granted = await navigator.storage.persist();
+			if (granted) {
+				console.log("✓ Persistent storage granted - sessions will be preserved");
+			} else {
+				console.warn("⚠ Browser denied persistent storage - sessions may be lost under storage pressure");
+			}
+			return granted;
+		} catch (error) {
+			console.error("Failed to request persistent storage:", error);
+			return false;
+		}
+	}
+
+	private handleGrant() {
+		if (this.resolvePromise) {
+			this.resolvePromise(true);
+			this.resolvePromise = undefined;
+		}
+		this.close();
+	}
+
+	private handleDeny() {
+		if (this.resolvePromise) {
+			this.resolvePromise(false);
+			this.resolvePromise = undefined;
+		}
+		this.close();
+	}
+
+	override close() {
+		super.close();
+		if (this.resolvePromise) {
+			this.resolvePromise(false);
+		}
+	}
+
+	protected override renderContent() {
+		return html`
+			${DialogContent({
+				children: html`
+					${DialogHeader({
+						title: i18n("Storage Permission Required"),
+						description: i18n("This app needs persistent storage to save your conversations"),
+					})}
+
+					<div class="mt-4 flex flex-col gap-4">
+						<div class="flex gap-3 p-4 bg-warning/10 border border-warning/20 rounded-lg">
+							<div class="flex-shrink-0 text-warning">
+								<svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+									<path d="M10.29 3.86L1.82 18a2 2 0 0 0 1.71 3h16.94a2 2 0 0 0 1.71-3L13.71 3.86a2 2 0 0 0-3.42 0z"></path>
+									<line x1="12" y1="9" x2="12" y2="13"></line>
+									<line x1="12" y1="17" x2="12.01" y2="17"></line>
+								</svg>
+							</div>
+							<div class="text-sm">
+								<p class="font-medium text-foreground mb-1">${i18n("Why is this needed?")}</p>
+								<p class="text-muted-foreground">
+									${i18n(
+										"Without persistent storage, your browser may delete saved conversations when it needs disk space. Granting this permission ensures your chat history is preserved.",
+									)}
+								</p>
+							</div>
+						</div>
+
+						<div class="text-sm text-muted-foreground">
+							<p class="mb-2">${i18n("What this means:")}</p>
+							<ul class="list-disc list-inside space-y-1 ml-2">
+								<li>${i18n("Your conversations will be saved locally in your browser")}</li>
+								<li>${i18n("Data will not be deleted automatically to free up space")}</li>
+								<li>${i18n("You can still manually clear data at any time")}</li>
+								<li>${i18n("No data is sent to external servers")}</li>
+							</ul>
+						</div>
+					</div>
+
+					<div class="mt-6 flex gap-3 justify-end">
+						${Button({
+							variant: "outline",
+							onClick: () => this.handleDeny(),
+							disabled: this.requesting,
+							children: i18n("Continue Anyway"),
+						})}
+						${Button({
+							variant: "default",
+							onClick: () => this.handleGrant(),
+							disabled: this.requesting,
+							children: this.requesting ? i18n("Requesting...") : i18n("Grant Permission"),
+						})}
+					</div>
+				`,
+			})}
+		`;
+	}
+}

packages/web-ui/src/dialogs/SessionListDialog.ts

@@ -0,0 +1,135 @@
+import { DialogBase, DialogContent, DialogHeader, html } from "@mariozechner/mini-lit";
+import { customElement, state } from "lit/decorators.js";
+import { getAppStorage } from "../storage/app-storage.js";
+import type { SessionMetadata } from "../storage/types.js";
+import { formatUsage } from "../utils/format.js";
+import { i18n } from "../utils/i18n.js";
+
+@customElement("session-list-dialog")
+export class SessionListDialog extends DialogBase {
+	@state() private sessions: SessionMetadata[] = [];
+	@state() private loading = true;
+
+	private onSelectCallback?: (sessionId: string) => void;
+
+	protected modalWidth = "min(600px, 90vw)";
+	protected modalHeight = "min(700px, 90vh)";
+
+	static async open(onSelect: (sessionId: string) => void) {
+		const dialog = new SessionListDialog();
+		dialog.onSelectCallback = onSelect;
+		dialog.open();
+		await dialog.loadSessions();
+	}
+
+	private async loadSessions() {
+		this.loading = true;
+		try {
+			const storage = getAppStorage();
+			if (!storage.sessions) {
+				console.error("Session storage not available");
+				this.sessions = [];
+				return;
+			}
+
+			this.sessions = await storage.sessions.listSessions();
+		} catch (err) {
+			console.error("Failed to load sessions:", err);
+			this.sessions = [];
+		} finally {
+			this.loading = false;
+		}
+	}
+
+	private async handleDelete(sessionId: string, event: Event) {
+		event.stopPropagation();
+
+		if (!confirm(i18n("Delete this session?"))) {
+			return;
+		}
+
+		try {
+			const storage = getAppStorage();
+			if (!storage.sessions) return;
+
+			await storage.sessions.deleteSession(sessionId);
+			await this.loadSessions();
+		} catch (err) {
+			console.error("Failed to delete session:", err);
+		}
+	}
+
+	private handleSelect(sessionId: string) {
+		if (this.onSelectCallback) {
+			this.onSelectCallback(sessionId);
+		}
+		this.close();
+	}
+
+	private formatDate(isoString: string): string {
+		const date = new Date(isoString);
+		const now = new Date();
+		const diff = now.getTime() - date.getTime();
+		const days = Math.floor(diff / (1000 * 60 * 60 * 24));
+
+		if (days === 0) {
+			return i18n("Today");
+		} else if (days === 1) {
+			return i18n("Yesterday");
+		} else if (days < 7) {
+			return i18n("{days} days ago").replace("{days}", days.toString());
+		} else {
+			return date.toLocaleDateString();
+		}
+	}
+
+	protected override renderContent() {
+		return html`
+			${DialogContent({
+				className: "h-full flex flex-col",
+				children: html`
+					${DialogHeader({
+						title: i18n("Sessions"),
+						description: i18n("Load a previous conversation"),
+					})}
+
+					<div class="flex-1 overflow-y-auto mt-4 space-y-2">
+						${
+							this.loading
+								? html`<div class="text-center py-8 text-muted-foreground">${i18n("Loading...")}</div>`
+								: this.sessions.length === 0
+									? html`<div class="text-center py-8 text-muted-foreground">${i18n("No sessions yet")}</div>`
+									: this.sessions.map(
+											(session) => html`
+											<div
+												class="group flex items-start gap-3 p-3 rounded-lg border border-border hover:bg-secondary/50 cursor-pointer transition-colors"
+												@click=${() => this.handleSelect(session.id)}
+											>
+												<div class="flex-1 min-w-0">
+													<div class="font-medium text-sm text-foreground truncate">${session.title}</div>
+													<div class="text-xs text-muted-foreground mt-1">${this.formatDate(session.lastModified)}</div>
+													<div class="text-xs text-muted-foreground mt-1">
+														${session.messageCount} ${i18n("messages")} · ${formatUsage(session.usage)}
+													</div>
+												</div>
+												<button
+													class="opacity-0 group-hover:opacity-100 p-1 rounded hover:bg-destructive/10 text-destructive transition-opacity"
+													@click=${(e: Event) => this.handleDelete(session.id, e)}
+													title=${i18n("Delete")}
+												>
+													<svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2">
+														<path d="M3 6h18"></path>
+														<path d="M19 6v14c0 1-1 2-2 2H7c-1 0-2-1-2-2V6"></path>
+														<path d="M8 6V4c0-1 1-2 2-2h4c1 0 2 1 2 2v2"></path>
+													</svg>
+												</button>
+											</div>
+										`,
+										)
+						}
+					</div>
+				`,
+			})}
+		`;
+	}
+}