feat: two-row tab bar with temp/persistent subagent tabs, tab persistence

- Split tab bar into user tabs (top) and subagent tabs (bottom row)
- Bottom row only visible when active user tab has child agents
- Parent user tab stays highlighted when viewing a subagent tab
- Temp tabs auto-disappear when agent completes, click to promote to persistent
- 'Open Tab' button on summon tool calls to view/reopen subagent history
- Reopening archived tabs fetches full chat history from backend
- Add parent_tab_id column to DB with safe ALTER TABLE migration
- Persist keyId, modelId, parentTabId on child tab creation
- Flush partial assistant messages on abort/error (finally block)
- Defensive JSON.parse in message restoration
- Allow all Vite hosts for local development
- Fix nested button in ToolCallDisplay (button inside button)

3 files changed, 82 insertions, 23 deletions

diff --git a/packages/core/src/db/index.ts b/packages/core/src/db/index.ts
index 2992708..81b474e 100644
--- a/packages/core/src/db/index.ts
+++ b/packages/core/src/db/index.ts
@@ -1,7 +1,7 @@
 import { Database } from "bun:sqlite";
 import { existsSync, mkdirSync } from "node:fs";
-import { isAbsolute, join } from "node:path";
 import { homedir } from "node:os";
+import { isAbsolute, join } from "node:path";
 
 /**
  * Returns the directory for persistent Dispatch data, following XDG Base
@@ -75,17 +75,24 @@ export function getDatabase(): Database {
 	)`);
 
 	_db.run(`CREATE TABLE IF NOT EXISTS tabs (
-		id          TEXT PRIMARY KEY,
-		title       TEXT NOT NULL,
-		key_id      TEXT,
-		model_id    TEXT,
-		status      TEXT NOT NULL DEFAULT 'idle',
-		is_open     INTEGER NOT NULL DEFAULT 1,
-		position    INTEGER NOT NULL DEFAULT 0,
-		created_at  INTEGER NOT NULL,
-		updated_at  INTEGER NOT NULL
+		id             TEXT PRIMARY KEY,
+		title          TEXT NOT NULL,
+		key_id         TEXT,
+		model_id       TEXT,
+		parent_tab_id  TEXT,
+		status         TEXT NOT NULL DEFAULT 'idle',
+		is_open        INTEGER NOT NULL DEFAULT 1,
+		position       INTEGER NOT NULL DEFAULT 0,
+		created_at     INTEGER NOT NULL,
+		updated_at     INTEGER NOT NULL
 	)`);
 
+	try {
+		_db.run("ALTER TABLE tabs ADD COLUMN parent_tab_id TEXT");
+	} catch {
+		// Column already exists — ignore
+	}
+
 	_db.run(`CREATE TABLE IF NOT EXISTS messages (
 		id           TEXT PRIMARY KEY,
 		tab_id       TEXT NOT NULL REFERENCES tabs(id),
diff --git a/packages/core/src/db/tabs.ts b/packages/core/src/db/tabs.ts
index 0f4511f..c0ce809 100644
--- a/packages/core/src/db/tabs.ts
+++ b/packages/core/src/db/tabs.ts
@@ -5,6 +5,7 @@ export interface TabRow {
 	title: string;
 	keyId: string | null;
 	modelId: string | null;
+	parentTabId: string | null;
 	status: string;
 	isOpen: boolean;
 	position: number;
@@ -18,6 +19,7 @@ function rowToTab(row: Record<string, unknown>): TabRow {
 		title: row.title as string,
 		keyId: row.key_id as string | null,
 		modelId: row.model_id as string | null,
+		parentTabId: (row.parent_tab_id as string) ?? null,
 		status: row.status as string,
 		isOpen: (row.is_open as number) === 1,
 		position: row.position as number,
@@ -26,48 +28,97 @@ function rowToTab(row: Record<string, unknown>): TabRow {
 	};
 }
 
-export function createTab(id: string, title: string): TabRow {
+export function createTab(
+	id: string,
+	title: string,
+	options?: { keyId?: string | null; modelId?: string | null; parentTabId?: string | null },
+): TabRow {
 	const db = getDatabase();
 	const now = Date.now();
-	const maxPos = db.query("SELECT COALESCE(MAX(position), -1) as max_pos FROM tabs WHERE is_open = 1").get() as { max_pos: number };
+	const maxPos = db
+		.query("SELECT COALESCE(MAX(position), -1) as max_pos FROM tabs WHERE is_open = 1")
+		.get() as { max_pos: number };
 	const position = (maxPos?.max_pos ?? -1) + 1;
+	const keyId = options?.keyId ?? null;
+	const modelId = options?.modelId ?? null;
+	const parentTabId = options?.parentTabId ?? null;
 	db.query(
-		`INSERT INTO tabs (id, title, key_id, model_id, status, is_open, position, created_at, updated_at)
-		 VALUES ($id, $title, NULL, NULL, 'idle', 1, $position, $now, $now)`,
-	).run({ $id: id, $title: title, $position: position, $now: now });
-	return { id, title, keyId: null, modelId: null, status: "idle", isOpen: true, position, createdAt: now, updatedAt: now };
+		`INSERT INTO tabs (id, title, key_id, model_id, parent_tab_id, status, is_open, position, created_at, updated_at)
+		 VALUES ($id, $title, $keyId, $modelId, $parentTabId, 'idle', 1, $position, $now, $now)`,
+	).run({
+		$id: id,
+		$title: title,
+		$keyId: keyId,
+		$modelId: modelId,
+		$parentTabId: parentTabId,
+		$position: position,
+		$now: now,
+	});
+	return {
+		id,
+		title,
+		keyId,
+		modelId,
+		parentTabId,
+		status: "idle",
+		isOpen: true,
+		position,
+		createdAt: now,
+		updatedAt: now,
+	};
 }
 
 export function getTab(id: string): TabRow | null {
 	const db = getDatabase();
-	const row = db.query("SELECT * FROM tabs WHERE id = $id").get({ $id: id }) as Record<string, unknown> | null;
+	const row = db.query("SELECT * FROM tabs WHERE id = $id").get({ $id: id }) as Record<
+		string,
+		unknown
+	> | null;
 	return row ? rowToTab(row) : null;
 }
 
 export function listOpenTabs(): TabRow[] {
 	const db = getDatabase();
-	const rows = db.query("SELECT * FROM tabs WHERE is_open = 1 ORDER BY position ASC").all() as Array<Record<string, unknown>>;
+	const rows = db
+		.query("SELECT * FROM tabs WHERE is_open = 1 ORDER BY position ASC")
+		.all() as Array<Record<string, unknown>>;
 	return rows.map(rowToTab);
 }
 
 export function updateTabTitle(id: string, title: string): void {
 	const db = getDatabase();
-	db.query("UPDATE tabs SET title = $title, updated_at = $now WHERE id = $id").run({ $id: id, $title: title, $now: Date.now() });
+	db.query("UPDATE tabs SET title = $title, updated_at = $now WHERE id = $id").run({
+		$id: id,
+		$title: title,
+		$now: Date.now(),
+	});
 }
 
 export function updateTabModel(id: string, keyId: string | null, modelId: string | null): void {
 	const db = getDatabase();
-	db.query("UPDATE tabs SET key_id = $keyId, model_id = $modelId, updated_at = $now WHERE id = $id").run({
-		$id: id, $keyId: keyId, $modelId: modelId, $now: Date.now(),
+	db.query(
+		"UPDATE tabs SET key_id = $keyId, model_id = $modelId, updated_at = $now WHERE id = $id",
+	).run({
+		$id: id,
+		$keyId: keyId,
+		$modelId: modelId,
+		$now: Date.now(),
 	});
 }
 
 export function updateTabStatus(id: string, status: string): void {
 	const db = getDatabase();
-	db.query("UPDATE tabs SET status = $status, updated_at = $now WHERE id = $id").run({ $id: id, $status: status, $now: Date.now() });
+	db.query("UPDATE tabs SET status = $status, updated_at = $now WHERE id = $id").run({
+		$id: id,
+		$status: status,
+		$now: Date.now(),
+	});
 }
 
 export function archiveTab(id: string): void {
 	const db = getDatabase();
-	db.query("UPDATE tabs SET is_open = 0, updated_at = $now WHERE id = $id").run({ $id: id, $now: Date.now() });
+	db.query("UPDATE tabs SET is_open = 0, updated_at = $now WHERE id = $id").run({
+		$id: id,
+		$now: Date.now(),
+	});
 }
diff --git a/packages/core/src/types/index.ts b/packages/core/src/types/index.ts
index 8745bc7..eaf8669 100644
--- a/packages/core/src/types/index.ts
+++ b/packages/core/src/types/index.ts
@@ -46,6 +46,7 @@ export type AgentEvent =
 			title: string;
 			keyId: string | null;
 			modelId: string | null;
+			parentTabId: string | null;
 	  };
 
 // ─── Tool Types ──────────────────────────────────────────────────