feat: agent builder, CWD support, auto-save, UI polish, unavailable tool handling

- Agent Builder: full CRUD with card grid, drag-and-drop model reorder, edit/delete
- Auto-save on edit with 600ms debounce, AbortController for concurrency, fieldset disabled until name entered
- Agent definitions stored as TOML with cwd field, loaded from global/project dirs
- Working directory: per-tab CWD override in Chat Settings, agent default CWD, auto-create on first message
- CWD validation: check-dir endpoint with ~ expansion, real-time validity indicator
- Subagent CWD validated against parent's effective CWD using path.relative
- Unavailable tool calls: caught gracefully, shown as tool call with error badge, model retries
- UI: tab bar border radius, sidebar border removed, chat input ghost style, scroll-to-bottom rectangle
- Skills dir collapse uses CSS rotation, Model Choice renamed to Chat Settings, System Prompt view removed
- Reusable SkillsBrowser/ToolPermissions with external mode for Agent Builder
- ModelSelector: Agent/Manual toggle, agent list, Agent Settings link
- Page router, skills recursive scanning, bin/up gopass removed, docker volume mounts

2 files changed, 25 insertions, 5 deletions

diff --git a/packages/core/src/db/messages.ts b/packages/core/src/db/messages.ts
index 5a8758f..80a1f22 100644
--- a/packages/core/src/db/messages.ts
+++ b/packages/core/src/db/messages.ts
@@ -10,14 +10,30 @@ export interface MessageRow {
 	createdAt: number;
 }
 
-export function appendMessage(tabId: string, id: string, role: string, contentJson: string, thinking?: string): void {
+export function appendMessage(
+	tabId: string,
+	id: string,
+	role: string,
+	contentJson: string,
+	thinking?: string,
+): void {
 	const db = getDatabase();
-	const maxSeq = db.query("SELECT COALESCE(MAX(seq), -1) as max_seq FROM messages WHERE tab_id = $tabId").get({ $tabId: tabId }) as { max_seq: number };
+	const maxSeq = db
+		.query("SELECT COALESCE(MAX(seq), -1) as max_seq FROM messages WHERE tab_id = $tabId")
+		.get({ $tabId: tabId }) as { max_seq: number };
 	const seq = (maxSeq?.max_seq ?? -1) + 1;
 	db.query(
 		`INSERT INTO messages (id, tab_id, seq, role, content_json, thinking, created_at)
 		 VALUES ($id, $tabId, $seq, $role, $contentJson, $thinking, $now)`,
-	).run({ $id: id, $tabId: tabId, $seq: seq, $role: role, $contentJson: contentJson, $thinking: thinking ?? null, $now: Date.now() });
+	).run({
+		$id: id,
+		$tabId: tabId,
+		$seq: seq,
+		$role: role,
+		$contentJson: contentJson,
+		$thinking: thinking ?? null,
+		$now: Date.now(),
+	});
 }
 
 export function updateMessage(id: string, contentJson: string, thinking?: string): void {
@@ -29,7 +45,9 @@ export function updateMessage(id: string, contentJson: string, thinking?: string
 
 export function getMessagesForTab(tabId: string): MessageRow[] {
 	const db = getDatabase();
-	const rows = db.query("SELECT * FROM messages WHERE tab_id = $tabId ORDER BY seq ASC").all({ $tabId: tabId }) as Array<Record<string, unknown>>;
+	const rows = db
+		.query("SELECT * FROM messages WHERE tab_id = $tabId ORDER BY seq ASC")
+		.all({ $tabId: tabId }) as Array<Record<string, unknown>>;
 	return rows.map((row) => ({
 		id: row.id as string,
 		tabId: row.tab_id as string,
diff --git a/packages/core/src/db/settings.ts b/packages/core/src/db/settings.ts
index 51d6ea2..f9d152e 100644
--- a/packages/core/src/db/settings.ts
+++ b/packages/core/src/db/settings.ts
@@ -2,7 +2,9 @@ import { getDatabase } from "./index.js";
 
 export function getSetting(key: string): string | null {
 	const db = getDatabase();
-	const row = db.query("SELECT value FROM settings WHERE key = $key").get({ $key: key }) as { value: string } | null;
+	const row = db.query("SELECT value FROM settings WHERE key = $key").get({ $key: key }) as {
+		value: string;
+	} | null;
 	return row?.value ?? null;
 }