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

1 files changed, 12 insertions, 7 deletions

diff --git a/packages/core/src/credentials/api-keys.ts b/packages/core/src/credentials/api-keys.ts
index 5f92ffa..af5aa0e 100644
--- a/packages/core/src/credentials/api-keys.ts
+++ b/packages/core/src/credentials/api-keys.ts
@@ -33,9 +33,9 @@ export function setApiKey(keyId: string, provider: string, apiKey: string): void
  */
 export function getApiKey(keyId: string): string | null {
 	const db = getDatabase();
-	const row = db.query(
-		"SELECT api_key FROM api_keys WHERE key_id = $keyId",
-	).get({ $keyId: keyId }) as { api_key: string } | null;
+	const row = db
+		.query("SELECT api_key FROM api_keys WHERE key_id = $keyId")
+		.get({ $keyId: keyId }) as { api_key: string } | null;
 	return row?.api_key ?? null;
 }
 
@@ -57,11 +57,16 @@ export function deleteApiKey(keyId: string): void {
 /**
  * List all stored API keys with metadata (key value excluded for security).
  */
-export function listApiKeys(): Array<{ keyId: string; provider: string; importedAt: number; updatedAt: number }> {
+export function listApiKeys(): Array<{
+	keyId: string;
+	provider: string;
+	importedAt: number;
+	updatedAt: number;
+}> {
 	const db = getDatabase();
-	const rows = db.query(
-		"SELECT key_id, provider, imported_at, updated_at FROM api_keys ORDER BY key_id",
-	).all() as Array<Record<string, unknown>>;
+	const rows = db
+		.query("SELECT key_id, provider, imported_at, updated_at FROM api_keys ORDER BY key_id")
+		.all() as Array<Record<string, unknown>>;
 	return rows.map((row) => ({
 		keyId: row.key_id as string,
 		provider: row.provider as string,