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, 213 insertions, 0 deletions

diff --git a/packages/core/src/agents/index.ts b/packages/core/src/agents/index.ts
new file mode 100644
index 0000000..13f6244
--- /dev/null
+++ b/packages/core/src/agents/index.ts
@@ -0,0 +1 @@
+export { deleteAgent, getAgentDirs, loadAgents, saveAgent } from "./loader.js";
diff --git a/packages/core/src/agents/loader.ts b/packages/core/src/agents/loader.ts
new file mode 100644
index 0000000..ec29983
--- /dev/null
+++ b/packages/core/src/agents/loader.ts
@@ -0,0 +1,212 @@
+import * as fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { parse as parseTOML, stringify as stringifyTOML } from "smol-toml";
+import type { AgentDefinition, AgentModelEntry } from "../types/index.js";
+
+// ─── Helpers ─────────────────────────────────────────────────────
+
+/** Sanitize a slug to prevent path traversal */
+function sanitizeSlug(slug: string): string {
+	// Strip directory components and ensure only safe characters
+	const base = path.basename(slug);
+	const clean = base
+		.replace(/[^a-zA-Z0-9_-]/g, "-")
+		.replace(/-+/g, "-")
+		.replace(/^-|-$/g, "");
+	if (!clean) throw new Error("Invalid agent slug");
+	return clean;
+}
+
+// ─── Constants ───────────────────────────────────────────────────
+
+const GLOBAL_AGENTS_DIR = path.join(os.homedir(), ".config", "dispatch", "agents");
+
+function getProjectAgentsDir(projectDir: string): string {
+	return path.join(projectDir, ".dispatch", "agents");
+}
+
+// ─── Public API ──────────────────────────────────────────────────
+
+/**
+ * Returns the agent directories that exist or could exist.
+ * Always includes global. Includes project dir if projectDir is provided.
+ */
+export function getAgentDirs(
+	projectDir?: string,
+): Array<{ label: string; path: string; scope: string }> {
+	const dirs: Array<{ label: string; path: string; scope: string }> = [
+		{ label: "Global (~/.config/dispatch/agents)", path: GLOBAL_AGENTS_DIR, scope: "global" },
+	];
+	if (projectDir) {
+		dirs.push({
+			label: `.dispatch/agents (${path.basename(projectDir)})`,
+			path: getProjectAgentsDir(projectDir),
+			scope: projectDir,
+		});
+	}
+	return dirs;
+}
+
+/**
+ * Ensure the default global agent exists. Creates it if missing.
+ */
+function ensureDefaultAgent(): void {
+	const filePath = path.join(GLOBAL_AGENTS_DIR, "default.toml");
+	if (fs.existsSync(filePath)) return;
+
+	const defaultAgent: AgentDefinition = {
+		name: "Default",
+		description: "Default agent with all tools enabled",
+		skills: [],
+		tools: ["read", "edit", "bash", "summon"],
+		models: [],
+		scope: "global",
+		slug: "default",
+	};
+	saveAgent(defaultAgent);
+}
+
+/**
+ * Load all agent definitions from global + project directories.
+ * Auto-generates the default global agent if it doesn't exist.
+ */
+export function loadAgents(projectDir?: string): AgentDefinition[] {
+	ensureDefaultAgent();
+
+	const agents: AgentDefinition[] = [];
+
+	// Global agents
+	agents.push(...loadAgentsFromDir(GLOBAL_AGENTS_DIR, "global"));
+
+	// Project-scoped agents
+	if (projectDir) {
+		agents.push(...loadAgentsFromDir(getProjectAgentsDir(projectDir), projectDir));
+	}
+
+	return agents;
+}
+
+/**
+ * Save (create or update) an agent definition to a TOML file.
+ * The scope determines which directory:
+ *   - "global" -> ~/.config/dispatch/agents/
+ *   - any other string -> that directory path + /.dispatch/agents/
+ */
+export function saveAgent(agent: AgentDefinition): void {
+	if (agent.scope !== "global" && agent.scope.includes("..")) {
+		throw new Error("Invalid agent scope");
+	}
+	const dir = agent.scope === "global" ? GLOBAL_AGENTS_DIR : getProjectAgentsDir(agent.scope);
+
+	fs.mkdirSync(dir, { recursive: true });
+
+	const tomlContent: Record<string, unknown> = {
+		name: agent.name,
+		description: agent.description,
+		skills: agent.skills,
+		tools: agent.tools,
+	};
+
+	if (agent.cwd) {
+		tomlContent.cwd = agent.cwd;
+	}
+
+	// smol-toml handles [[models]] array-of-tables
+	if (agent.models.length > 0) {
+		tomlContent.models = agent.models.map((m) => ({
+			key_id: m.key_id,
+			model_id: m.model_id,
+		}));
+	}
+
+	const content = stringifyTOML(tomlContent);
+	const safeSlug = sanitizeSlug(agent.slug);
+	const filePath = path.join(dir, `${safeSlug}.toml`);
+	fs.writeFileSync(filePath, content, "utf-8");
+}
+
+/**
+ * Delete an agent TOML file.
+ */
+export function deleteAgent(slug: string, scope: string): boolean {
+	if (scope !== "global" && scope.includes("..")) {
+		throw new Error("Invalid agent scope");
+	}
+	const dir = scope === "global" ? GLOBAL_AGENTS_DIR : getProjectAgentsDir(scope);
+
+	const safeSlug = sanitizeSlug(slug);
+	const filePath = path.join(dir, `${safeSlug}.toml`);
+	if (fs.existsSync(filePath)) {
+		fs.unlinkSync(filePath);
+		return true;
+	}
+	return false;
+}
+
+// ─── Internal ────────────────────────────────────────────────────
+
+function loadAgentsFromDir(dir: string, scope: string): AgentDefinition[] {
+	if (!fs.existsSync(dir)) return [];
+
+	const results: AgentDefinition[] = [];
+	let entries: fs.Dirent[];
+	try {
+		entries = fs.readdirSync(dir, { withFileTypes: true });
+	} catch {
+		return [];
+	}
+
+	for (const entry of entries) {
+		if (!entry.isFile() || !entry.name.endsWith(".toml")) continue;
+
+		const filePath = path.join(dir, entry.name);
+		const slug = entry.name.slice(0, -5); // remove .toml
+
+		try {
+			const raw = fs.readFileSync(filePath, "utf-8");
+			const parsed = parseTOML(raw);
+
+			const models: AgentModelEntry[] = [];
+			if (Array.isArray(parsed.models)) {
+				for (const m of parsed.models) {
+					if (m && typeof m === "object" && "key_id" in m && "model_id" in m) {
+						models.push({
+							key_id: String((m as Record<string, unknown>).key_id),
+							model_id: String((m as Record<string, unknown>).model_id),
+						});
+					}
+				}
+			}
+
+			const skills: string[] = [];
+			if (Array.isArray(parsed.skills)) {
+				for (const s of parsed.skills) {
+					if (typeof s === "string") skills.push(s);
+				}
+			}
+
+			const tools: string[] = [];
+			if (Array.isArray(parsed.tools)) {
+				for (const t of parsed.tools) {
+					if (typeof t === "string") tools.push(t);
+				}
+			}
+
+			results.push({
+				name: typeof parsed.name === "string" ? parsed.name : slug,
+				description: typeof parsed.description === "string" ? parsed.description : "",
+				skills,
+				tools,
+				models,
+				scope,
+				slug,
+				...(typeof parsed.cwd === "string" && parsed.cwd ? { cwd: parsed.cwd } : {}),
+			});
+		} catch {
+			// Skip unparseable files
+		}
+	}
+
+	return results;
+}