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, 20 insertions, 12 deletions

diff --git a/packages/frontend/tests/chat-store.test.ts b/packages/frontend/tests/chat-store.test.ts
index a56ac13..978bce1 100644
--- a/packages/frontend/tests/chat-store.test.ts
+++ b/packages/frontend/tests/chat-store.test.ts
@@ -87,15 +87,15 @@ function createTestStore(wsSend?: (data: unknown) => void) {
 				ensureCurrentAssistantMessage();
 				messages = messages.map((m) => {
 					if (m.id === currentAssistantId) {
-					const segments: ContentSegment[] = [
-						...m.content,
-						{
-							type: "tool-call",
-							id: event.toolCall.id,
-							name: event.toolCall.name,
-							arguments: event.toolCall.arguments,
-						},
-					];
+						const segments: ContentSegment[] = [
+							...m.content,
+							{
+								type: "tool-call",
+								id: event.toolCall.id,
+								name: event.toolCall.name,
+								arguments: event.toolCall.arguments,
+							},
+						];
 						return { ...m, content: segments };
 					}
 					return m;
@@ -109,7 +109,11 @@ function createTestStore(wsSend?: (data: unknown) => void) {
 							...m,
 							content: m.content.map((seg) => {
 								if (seg.type === "tool-call" && seg.id === event.toolResult.toolCallId) {
-									return { ...seg, result: event.toolResult.result, isError: event.toolResult.isError };
+									return {
+										...seg,
+										result: event.toolResult.result,
+										isError: event.toolResult.isError,
+									};
 								}
 								return seg;
 							}),
@@ -338,7 +342,9 @@ describe("chat store logic", () => {
 	it("error event adds an error message and sets status to error", () => {
 		store.handleEvent({ type: "error", error: "something went wrong" });
 		expect(store.messages).toHaveLength(1);
-		expect(store.messages[0]?.content).toEqual([{ type: "text", text: "Error: something went wrong" }]);
+		expect(store.messages[0]?.content).toEqual([
+			{ type: "text", text: "Error: something went wrong" },
+		]);
 		expect(store.agentStatus).toBe("error");
 	});
 
@@ -529,7 +535,9 @@ describe("permission log", () => {
 });
 
 // Shell output parsing logic (mirrors ToolCallDisplay logic)
-function parseShellResult(result: string): { stdout: string; stderr: string; exitCode: number } | null {
+function parseShellResult(
+	result: string,
+): { stdout: string; stderr: string; exitCode: number } | null {
 	try {
 		const parsed = JSON.parse(result) as unknown;
 		if (