feat(coding-agent): add session naming via /name command and extension API

- Add SessionInfoEntry type for session metadata
- Add /name <name> command to set session display name
- Add pi.setSessionName() and pi.getSessionName() extension API
- Session selector shows name (in warning color) instead of first message when set
- Session name included in fuzzy search
- /session command displays name when set

closes #650

packages/coding-agent/src/core/extensions/loader.ts

@@ -86,6 +86,8 @@ export function createExtensionRuntime(): ExtensionRuntime {
 		sendMessage: notInitialized,
 		sendUserMessage: notInitialized,
 		appendEntry: notInitialized,
+		setSessionName: notInitialized,
+		getSessionName: notInitialized,
 		getActiveTools: notInitialized,
 		getAllTools: notInitialized,
 		setActiveTools: notInitialized,
@@ -169,6 +171,14 @@ function createExtensionAPI(
 			runtime.appendEntry(customType, data);
 		},
 
+		setSessionName(name: string): void {
+			runtime.setSessionName(name);
+		},
+
+		getSessionName(): string | undefined {
+			return runtime.getSessionName();
+		},
+
 		exec(command: string, args: string[], options?: ExecOptions) {
 			return execCommand(command, args, options?.cwd ?? cwd, options);
 		},

packages/coding-agent/src/core/extensions/runner.ts

@@ -140,6 +140,8 @@ export class ExtensionRunner {
 		this.runtime.sendMessage = actions.sendMessage;
 		this.runtime.sendUserMessage = actions.sendUserMessage;
 		this.runtime.appendEntry = actions.appendEntry;
+		this.runtime.setSessionName = actions.setSessionName;
+		this.runtime.getSessionName = actions.getSessionName;
 		this.runtime.getActiveTools = actions.getActiveTools;
 		this.runtime.getAllTools = actions.getAllTools;
 		this.runtime.setActiveTools = actions.setActiveTools;

packages/coding-agent/src/core/extensions/types.ts

@@ -727,6 +727,16 @@ export interface ExtensionAPI {
 	/** Append a custom entry to the session for state persistence (not sent to LLM). */
 	appendEntry<T = unknown>(customType: string, data?: T): void;
 
+	// =========================================================================
+	// Session Metadata
+	// =========================================================================
+
+	/** Set the session display name (shown in session selector). */
+	setSessionName(name: string): void;
+
+	/** Get the current session name, if set. */
+	getSessionName(): string | undefined;
+
 	/** Execute a shell command. */
 	exec(command: string, args: string[], options?: ExecOptions): Promise<ExecResult>;
 
@@ -797,6 +807,10 @@ export type SendUserMessageHandler = (
 
 export type AppendEntryHandler = <T = unknown>(customType: string, data?: T) => void;
 
+export type SetSessionNameHandler = (name: string) => void;
+
+export type GetSessionNameHandler = () => string | undefined;
+
 export type GetActiveToolsHandler = () => string[];
 
 export type GetAllToolsHandler = () => string[];
@@ -825,6 +839,8 @@ export interface ExtensionActions {
 	sendMessage: SendMessageHandler;
 	sendUserMessage: SendUserMessageHandler;
 	appendEntry: AppendEntryHandler;
+	setSessionName: SetSessionNameHandler;
+	getSessionName: GetSessionNameHandler;
 	getActiveTools: GetActiveToolsHandler;
 	getAllTools: GetAllToolsHandler;
 	setActiveTools: SetActiveToolsHandler;