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

3 files changed, 60 insertions, 43 deletions

diff --git a/packages/core/src/tools/bash-arity.ts b/packages/core/src/tools/bash-arity.ts
index 5dde955..1aaba8e 100644
--- a/packages/core/src/tools/bash-arity.ts
+++ b/packages/core/src/tools/bash-arity.ts
@@ -1,37 +1,37 @@
 // Hardcoded dictionary of well-known commands and their arity
 // (number of tokens that form the "human-understandable" prefix)
 const ARITY: Record<string, number> = {
-	"git": 2,        // "git checkout", "git commit", etc.
-	"npm": 3,        // "npm run dev", "npm install -g"
-	"docker": 2,     // "docker compose", "docker build"
-	"kubectl": 2,    // "kubectl get", "kubectl apply"
-	"bun": 2,        // "bun install", "bun test"
-	"cargo": 2,      // "cargo build", "cargo test"
-	"go": 2,         // "go build", "go test"
-	"python": 2,     // "python -m", "python script.py"
-	"python3": 2,
-	"pip": 2,
-	"pip3": 2,
-	"brew": 2,
-	"apt": 2,
+	git: 2, // "git checkout", "git commit", etc.
+	npm: 3, // "npm run dev", "npm install -g"
+	docker: 2, // "docker compose", "docker build"
+	kubectl: 2, // "kubectl get", "kubectl apply"
+	bun: 2, // "bun install", "bun test"
+	cargo: 2, // "cargo build", "cargo test"
+	go: 2, // "go build", "go test"
+	python: 2, // "python -m", "python script.py"
+	python3: 2,
+	pip: 2,
+	pip3: 2,
+	brew: 2,
+	apt: 2,
 	"apt-get": 2,
-	"dnf": 2,
-	"yum": 2,
-	"pacman": 2,
-	"systemctl": 2,
-	"journalctl": 2,
-	"ssh": 2,
-	"scp": 2,
-	"rsync": 2,
-	"curl": 2,       // "curl -X", "curl https://"
-	"wget": 2,
-	"tar": 2,        // "tar -xzf", "tar -czf"
-	"zip": 2,
-	"unzip": 2,
-	"chown": 2,
-	"chmod": 2,
-	"mount": 2,
-	"umount": 2,
+	dnf: 2,
+	yum: 2,
+	pacman: 2,
+	systemctl: 2,
+	journalctl: 2,
+	ssh: 2,
+	scp: 2,
+	rsync: 2,
+	curl: 2, // "curl -X", "curl https://"
+	wget: 2,
+	tar: 2, // "tar -xzf", "tar -czf"
+	zip: 2,
+	unzip: 2,
+	chown: 2,
+	chmod: 2,
+	mount: 2,
+	umount: 2,
 	// Default: all other commands are arity 1
 };
 
diff --git a/packages/core/src/tools/run-shell.ts b/packages/core/src/tools/run-shell.ts
index d549316..608c91d 100644
--- a/packages/core/src/tools/run-shell.ts
+++ b/packages/core/src/tools/run-shell.ts
@@ -11,12 +11,12 @@ export function createRunShellTool(workingDirectory: string): ToolDefinition {
 			"Execute a shell command in the working directory. Returns stdout, stderr, and exit code. Use for running tests, builds, git operations, package management, and other development tasks.",
 		parameters: z.object({
 			command: z.string().describe("The shell command to execute"),
-			timeout: z
-				.number()
-				.optional()
-				.describe("Timeout in milliseconds (default 2 minutes)"),
+			timeout: z.number().optional().describe("Timeout in milliseconds (default 2 minutes)"),
 		}),
-		execute: async (args: Record<string, unknown>, context?: ToolExecuteContext): Promise<string> => {
+		execute: async (
+			args: Record<string, unknown>,
+			context?: ToolExecuteContext,
+		): Promise<string> => {
 			const command = args.command as string;
 			const timeout = (args.timeout as number | undefined) ?? DEFAULT_TIMEOUT;
 
@@ -68,7 +68,5 @@ export function createRunShellTool(workingDirectory: string): ToolDefinition {
 }
 
 function getShell(): [string, string[]] {
-	return process.platform === "win32"
-		? ["powershell", ["-Command"]]
-		: ["bash", ["-c"]];
+	return process.platform === "win32" ? ["powershell", ["-Command"]] : ["bash", ["-c"]];
 }
diff --git a/packages/core/src/tools/shell-analyze.ts b/packages/core/src/tools/shell-analyze.ts
index 23bbfc9..b70108b 100644
--- a/packages/core/src/tools/shell-analyze.ts
+++ b/packages/core/src/tools/shell-analyze.ts
@@ -1,6 +1,6 @@
-import { dirname, isAbsolute, relative, resolve, sep } from "node:path";
 import { readFile } from "node:fs/promises";
 import { createRequire } from "node:module";
+import { dirname, isAbsolute, relative, resolve, sep } from "node:path";
 import * as BashArity from "./bash-arity.js";
 
 // Commands that touch files — triggers external_directory check.
@@ -12,9 +12,27 @@ import * as BashArity from "./bash-arity.js";
 //   - `cd` state changes: we don't track cwd mutations across pipeline stages
 //   - Interpreter escapes: `python -c "open('/etc/passwd')"`, `node -e "..."` bypass this entirely
 const FILE_COMMANDS = new Set([
-	"rm", "cp", "mv", "mkdir", "touch", "chmod", "chown",
-	"cat", "ls", "find", "grep",
-	"head", "tail", "less", "more", "wc", "diff", "file", "stat", "du", "df",
+	"rm",
+	"cp",
+	"mv",
+	"mkdir",
+	"touch",
+	"chmod",
+	"chown",
+	"cat",
+	"ls",
+	"find",
+	"grep",
+	"head",
+	"tail",
+	"less",
+	"more",
+	"wc",
+	"diff",
+	"file",
+	"stat",
+	"du",
+	"df",
 ]);
 
 // Lazy-initialized parser
@@ -142,6 +160,7 @@ function isInsideWorkspace(filePath: string, wd: string): boolean {
 	// rel === "" means filePath IS the workspace root — that is inside.
 	// If relative path starts with "../" or is ".." exactly, or is an absolute path
 	// (on Windows when drives differ), the file is outside the workspace.
-	const isOutside = rel.startsWith(`..${sep}`) || rel.startsWith("../") || rel === ".." || isAbsolute(rel);
+	const isOutside =
+		rel.startsWith(`..${sep}`) || rel.startsWith("../") || rel === ".." || isAbsolute(rel);
 	return !isOutside;
 }