feat: canonical workspace tab IDs with URL routing and draft agent tabs

Rewrite workspace tab management to use stable tab IDs (agent_, terminal_, draft_, file_) with
dedicated /tab/[tabId] routes, replace separate file-tabs store with unified workspace-tabs store,
support multiple concurrent draft agent tabs, and detect text files by content instead of extension allowlist.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/screens/agent/agent-ready-screen.tsx

@@ -436,16 +436,28 @@ function AgentScreenContent({
   );
   const streamItems = streamItemsRaw ?? EMPTY_STREAM_ITEMS;
 
-  const pendingCreate = useCreateFlowStore((state) => state.pending);
+  const pendingByDraftId = useCreateFlowStore((state) => state.pendingByDraftId);
   const markPendingCreateLifecycle = useCreateFlowStore(
     (state) => state.markLifecycle
   );
   const clearPendingCreate = useCreateFlowStore((state) => state.clear);
-  const isPendingCreateForRoute =
-    Boolean(pendingCreate) &&
-    pendingCreate?.lifecycle === "active" &&
-    pendingCreate?.serverId === serverId &&
-    pendingCreate?.agentId === resolvedAgentId;
+  const pendingCreate = useMemo(() => {
+    if (!resolvedAgentId) {
+      return null;
+    }
+    const values = Object.values(pendingByDraftId);
+    for (const entry of values) {
+      if (
+        entry.lifecycle === "active" &&
+        entry.serverId === serverId &&
+        entry.agentId === resolvedAgentId
+      ) {
+        return entry;
+      }
+    }
+    return null;
+  }, [pendingByDraftId, resolvedAgentId, serverId]);
+  const isPendingCreateForRoute = Boolean(pendingCreate);
 
   // Select only the specific initializing state
   const isInitializingFromMap = useSessionStore((state) =>
@@ -740,7 +752,7 @@ function AgentScreenContent({
         item.kind === "user_message" &&
         item.id === pendingCreate.clientMessageId
     );
-    if (hasUserMessage && canFinalizePendingCreate) {
+      if (hasUserMessage && canFinalizePendingCreate) {
       if (
         resolvedAgentId &&
         pendingCreate.images &&
@@ -766,8 +778,8 @@ function AgentScreenContent({
           return next;
         });
       }
-      markPendingCreateLifecycle("sent");
-      clearPendingCreate();
+      markPendingCreateLifecycle({ draftId: pendingCreate.draftId, lifecycle: "sent" });
+      clearPendingCreate({ draftId: pendingCreate.draftId });
     }
   }, [
     canFinalizePendingCreate,

packages/app/src/screens/agent/draft-agent-screen.tsx

@@ -51,6 +51,7 @@ import { AGENT_PROVIDER_DEFINITIONS } from '@server/server/agent/provider-manife
 import { buildHostAgentDetailRoute } from '@/utils/host-routes'
 import { useTauriDragHandlers } from '@/utils/tauri-window'
 import { useKeyboardShiftStyle } from '@/hooks/use-keyboard-shift-style'
+import { normalizeAgentSnapshot } from '@/utils/agent-snapshots'
 
 const DRAFT_AGENT_ID = '__new_agent__'
 const EMPTY_PENDING_PERMISSIONS = new Map()
@@ -1023,9 +1024,15 @@ function DraftAgentScreenContent({
           git: gitOptions,
         })
 
-        const agentId = (result as { id?: string })?.id
+        const agentId = result.id
         if (agentId && selectedServerId) {
-          updatePendingAgentId(agentId)
+          updatePendingAgentId({ draftId: draftIdRef.current, agentId })
+          useSessionStore.getState().setAgents(selectedServerId, (prev) => {
+            const next = new Map(prev)
+            next.set(agentId, normalizeAgentSnapshot(result, selectedServerId))
+            return next
+          })
+          void createAgentClient.refreshAgent(agentId).catch(() => undefined)
           router.replace(buildHostAgentDetailRoute(selectedServerId, agentId) as any)
           return
         }
@@ -1035,15 +1042,15 @@ function DraftAgentScreenContent({
           message: 'Failed to create agent',
         })
         onCreateFlowActiveChange?.(false)
-        markPendingCreateLifecycle('abandoned')
-        clearPendingCreateAttempt()
+        markPendingCreateLifecycle({ draftId: draftIdRef.current, lifecycle: 'abandoned' })
+        clearPendingCreateAttempt({ draftId: draftIdRef.current })
         throw new Error('Failed to create agent')
       } catch (error) {
         const message = error instanceof Error ? error.message : 'Failed to create agent'
         dispatch({ type: 'CREATE_FAILED', message })
         onCreateFlowActiveChange?.(false)
-        markPendingCreateLifecycle('abandoned')
-        clearPendingCreateAttempt()
+        markPendingCreateLifecycle({ draftId: draftIdRef.current, lifecycle: 'abandoned' })
+        clearPendingCreateAttempt({ draftId: draftIdRef.current })
         throw error // Re-throw so AgentInputArea knows it failed
       }
     },