Fix tests for sessionManager/modelRegistry on context

- compaction-hooks-example.test.ts: get sessionManager/modelRegistry from ctx
- compaction-hooks.test.ts:
  - Pass sessionManager/modelRegistry to HookRunner constructor
  - Remove setSessionFile call
  - Update tests to use session.sessionManager instead of event.sessionManager

packages/coding-agent/src/core/custom-tools/loader.ts

@@ -298,7 +298,8 @@ export async function loadCustomTools(
 	// Shared API object - all tools get the same instance
 	const sharedApi: ToolAPI = {
 		cwd,
-		exec: (command: string, args: string[], options?: ExecOptions) => execCommand(command, args, cwd, options),
+		exec: (command: string, args: string[], options?: ExecOptions) =>
+			execCommand(command, args, options?.cwd ?? cwd, options),
 		ui: createNoOpUIContext(),
 		hasUI: false,
 	};

packages/coding-agent/src/core/custom-tools/types.ts

@@ -31,6 +31,8 @@ export interface ExecOptions {
 	signal?: AbortSignal;
 	/** Timeout in milliseconds */
 	timeout?: number;
+	/** Working directory */
+	cwd?: string;
 }
 
 /** API passed to custom tool factory (stable across session changes) */