Key workspace status and ownership by ID, not directory

Multiple workspaces can share one checkout directory. Agent and terminal
status, sidebar tabs, and ownership now attribute strictly by workspace ID,
so a running or blocked agent in one workspace no longer shows up on its
same-directory siblings.

A one-time startup migration backfills workspace IDs onto legacy agents, and
every agent and terminal is created with one thereafter. Directory lookups
remain only for genuinely folder-derived git facts (branch, diff) and the
archive-by-path adapter.

packages/server/src/terminal/terminal-manager.ts

@@ -16,7 +16,7 @@ export interface TerminalListItem {
   id: string;
   name: string;
   cwd: string;
-  workspaceId?: string;
+  workspaceId: string;
   title?: string;
   activity: TerminalActivity | null;
 }
@@ -32,6 +32,7 @@ export interface TerminalActivityTransitionEvent {
   terminalId: string;
   name: string;
   cwd: string;
+  workspaceId: string;
   activity: TerminalActivity | null;
   previous: TerminalActivity | null;
 }
@@ -41,7 +42,7 @@ export type TerminalActivityListener = (event: TerminalActivityTransitionEvent)
 export interface TerminalWorkspaceContributionChangedEvent {
   terminalId: string;
   cwd: string;
-  workspaceId?: string;
+  workspaceId: string;
 }
 
 export type TerminalWorkspaceContributionChangedListener = (
@@ -53,7 +54,7 @@ export interface TerminalManager {
   createTerminal(options: {
     id?: string;
     cwd: string;
-    workspaceId?: string;
+    workspaceId: string;
     name?: string;
     title?: string;
     env?: Record<string, string>;
@@ -159,7 +160,7 @@ export function createTerminalManager(
       emitTerminalWorkspaceContributionChanged({
         terminalId: session.id,
         cwd: session.cwd,
-        ...(session.workspaceId ? { workspaceId: session.workspaceId } : {}),
+        workspaceId: session.workspaceId,
       });
     }
 
@@ -200,7 +201,7 @@ export function createTerminalManager(
         emitTerminalWorkspaceContributionChanged({
           terminalId: session.id,
           cwd: session.cwd,
-          ...(session.workspaceId ? { workspaceId: session.workspaceId } : {}),
+          workspaceId: session.workspaceId,
         });
       }
     });
@@ -215,7 +216,7 @@ export function createTerminalManager(
       id: input.session.id,
       name: input.session.name,
       cwd: input.session.cwd,
-      ...(input.session.workspaceId ? { workspaceId: input.session.workspaceId } : {}),
+      workspaceId: input.session.workspaceId,
       title: input.session.getTitle(),
       activity: input.session.getActivity(),
     };
@@ -254,6 +255,7 @@ export function createTerminalManager(
       terminalId: input.session.id,
       name: input.session.name,
       cwd: input.session.cwd,
+      workspaceId: input.session.workspaceId,
       activity: input.transition.activity,
       previous: input.transition.previous,
     };
@@ -307,7 +309,7 @@ export function createTerminalManager(
     async createTerminal(options: {
       id?: string;
       cwd: string;
-      workspaceId?: string;
+      workspaceId: string;
       name?: string;
       title?: string;
       env?: Record<string, string>;
@@ -341,7 +343,7 @@ export function createTerminalManager(
           await createTerminal({
             id: terminalId,
             cwd: options.cwd,
-            ...(options.workspaceId ? { workspaceId: options.workspaceId } : {}),
+            workspaceId: options.workspaceId,
             name: options.name ?? defaultName,
             ...(options.title ? { title: options.title } : {}),
             ...(options.command ? { command: options.command } : {}),