fix(coding-agent): persisted vibe sessions across restarts

Vibe worker roster lived only in a process-local Map, so a resumed parent
session started with an empty registry and vibe_send failed with
"Unknown vibe session". Persist a versioned, parent-scoped lifecycle
journal (spawn/turn/tombstone events), rehydrate validated idle workers
through the persisted-subagent reviver on resume, and gate the flow with
generation/CAS protection so stale finalizers cannot clobber a
replacement worker. Killed transcripts stay readable but non-revivable;
mode-exit commits tombstones atomically with the mode change and rolls
back cleanly on storage failure.

Ported from @mastertyko's fork branch fix/vibe-session-persistence.

Fixes #5303

packages/coding-agent/src/modes/controllers/command-controller.ts

@@ -992,7 +992,7 @@ export class CommandController {
 		}
 
 		try {
-			await this.ctx.sessionManager.moveTo(resolvedPath);
+			await this.ctx.session.moveSession(resolvedPath);
 		} catch (err) {
 			this.ctx.showError(`Move failed: ${err instanceof Error ? err.message : String(err)}`);
 			return;