Rework custom tools API with CustomToolContext

- CustomAgentTool renamed to CustomTool
- ToolAPI renamed to CustomToolAPI
- ToolContext renamed to CustomToolContext
- ToolSessionEvent renamed to CustomToolSessionEvent
- Added CustomToolContext parameter to execute() and onSession()
- CustomToolFactory now returns CustomTool<any, any> for type compatibility
- dispose() replaced with onSession({ reason: 'shutdown' })
- Added wrapCustomTool() to convert CustomTool to AgentTool
- Session exposes setToolUIContext() instead of leaking internals
- Fix ToolExecutionComponent to sync with toolOutputExpanded state
- Update all custom tool examples for new API

packages/coding-agent/src/core/session-manager.ts

@@ -159,19 +159,21 @@ export interface SessionInfo {
 	allMessagesText: string;
 }
 
-/**
- * Read-only interface for SessionManager.
- * Used by compaction/summarization utilities that only need to read session data.
- */
-export interface ReadonlySessionManager {
-	getLeafId(): string | null;
-	getEntry(id: string): SessionEntry | undefined;
-	getPath(fromId?: string): SessionEntry[];
-	getEntries(): SessionEntry[];
-	getChildren(parentId: string): SessionEntry[];
-	getTree(): SessionTreeNode[];
-	getLabel(id: string): string | undefined;
-}
+export type ReadonlySessionManager = Pick<
+	SessionManager,
+	| "getCwd"
+	| "getSessionDir"
+	| "getSessionId"
+	| "getSessionFile"
+	| "getLeafId"
+	| "getLeafEntry"
+	| "getEntry"
+	| "getLabel"
+	| "getBranch"
+	| "getHeader"
+	| "getEntries"
+	| "getTree"
+>;
 
 /** Generate a unique short ID (8 hex chars, collision-checked) */
 function generateId(byId: { has(id: string): boolean }): string {
@@ -772,7 +774,7 @@ export class SessionManager {
 	 * Includes all entry types (messages, compaction, model changes, etc.).
 	 * Use buildSessionContext() to get the resolved messages for the LLM.
 	 */
-	getPath(fromId?: string): SessionEntry[] {
+	getBranch(fromId?: string): SessionEntry[] {
 		const path: SessionEntry[] = [];
 		const startId = fromId ?? this.leafId;
 		let current = startId ? this.byId.get(startId) : undefined;
@@ -908,7 +910,7 @@ export class SessionManager {
 	 * Returns the new session file path, or undefined if not persisting.
 	 */
 	createBranchedSession(leafId: string): string | undefined {
-		const path = this.getPath(leafId);
+		const path = this.getBranch(leafId);
 		if (path.length === 0) {
 			throw new Error(`Entry ${leafId} not found`);
 		}