feat: implement git_worktree_list tool

- Implement parseWorktreeList() to parse /home/david/Projects/extensions/pi-worktrees         e597520 [issue-1-tmp]
/home/david/Projects/extensions/pi-worktrees/issue-3 dd2202f [issue-3]
/home/david/Projects/extensions/pi-worktrees/main    dd2202f [main] output
  into structured WorktreeEntry[] with path, commit, branch, isCurrent
- Handle detached HEAD (no brackets → '(detached)')
- Wire the parser into git_worktree_list execute function
- Return formatted display text + structured details for downstream use
- Move tool definitions inside extension factory to capture  closure
- Add error handling with clear message when not in a git repo

.pi/extensions/pi-worktree.ts

@@ -71,12 +71,37 @@ const removeWorktreeParams = Type.Object({
 
 /**
  * Parse raw `git worktree list` output into structured entries.
+ *
+ * Expected format (whitespace-separated):
+ *   /path/to/repo    abc1234 [main]
+ *   /tmp/feature-x   def5678 [feature-x]
+ *   /tmp/detached    fedcba HEAD
+ *
  * @param rawOutput - Raw stdout from `git worktree list`
  * @param currentDir - Current working directory for comparison
  * @returns Array of parsed worktree entries
  */
 function parseWorktreeList(rawOutput: string, currentDir: string): WorktreeEntry[] {
-	throw new Error("not implemented");
+	const lines = rawOutput.trim().split("\n").filter((line) => line.trim());
+
+	return lines.map((line) => {
+		// Split on whitespace: path, commit_hash, [branch] or HEAD
+		const parts = line.trim().split(/\s+/);
+		const worktreePath = parts[0];
+		const commitHash = parts[1];
+		const branchRaw = parts.slice(2).join(" ");
+
+		// Extract branch name from brackets, or mark as detached
+		const bracketMatch = branchRaw.match(/^\[(.+)\]$/);
+		const branchName = bracketMatch ? bracketMatch[1] : "(detached)";
+
+		return {
+			path: worktreePath,
+			commit: commitHash,
+			branch: branchName,
+			isCurrent: worktreePath === currentDir,
+		};
+	});
 }
 
 /**
@@ -99,10 +124,13 @@ function resolveWorktreeTarget(target: string, worktrees: WorktreeEntry[]): stri
 	throw new Error("not implemented");
 }
 
-// ─── Tool Definitions ──────────────────────────────────────────────
+// ─── Extension Entry Point ────────────────────────────────────────
+
+export default function (pi: ExtensionAPI) {
+	// Register tools (defined here to capture `pi` via closure)
 
 	/** Create a linked worktree for a branch in the current repo. */
-const gitWorktreeCreateTool = defineTool({
+	pi.registerTool(defineTool({
 		name: "git_worktree_create",
 		label: "Git Worktree Create",
 		description: "Create a linked worktree for a branch in the current repo.",
@@ -113,24 +141,39 @@ const gitWorktreeCreateTool = defineTool({
 				isError: true,
 			};
 		},
-});
+	}));
 
 	/** List all linked worktrees in the current repo. */
-const gitWorktreeListTool = defineTool({
+	pi.registerTool(defineTool({
 		name: "git_worktree_list",
 		label: "Git Worktree List",
 		description: "List all linked worktrees in the current repo.",
 		parameters: listWorktreeParams,
-	async execute(_toolCallId, _params, _signal, _onUpdate, _ctx) {
+		async execute(_toolCallId, _params, _signal, _onUpdate, ctx) {
+			const result = await pi.exec("git", ["worktree", "list"], { cwd: ctx.cwd });
+
+			if (result.exitCode !== 0) {
 				return {
-			content: [{ type: "text", text: "Error: git_worktree_list is not yet implemented. Suggestion: Use `git worktree list` manually until this tool is complete." }],
+					content: [{ type: "text", text: `Error listing worktrees: ${result.stderr}. Suggestion: Ensure you are inside a git repository.` }],
 					isError: true,
 				};
+			}
+
+			const worktreeEntries = parseWorktreeList(result.stdout, ctx.cwd);
+
+			const displayLines = worktreeEntries.map(
+				(entry) => `${entry.branch} — ${entry.path}${entry.isCurrent ? " (current)" : ""}`,
+			);
+
+			return {
+				content: [{ type: "text", text: displayLines.join("\n") }],
+				details: { worktrees: worktreeEntries },
+			};
 		},
-});
+	}));
 
 	/** Switch pi's working directory to a linked worktree. */
-const gitWorktreeSwitchTool = defineTool({
+	pi.registerTool(defineTool({
 		name: "git_worktree_switch",
 		label: "Git Worktree Switch",
 		description: "Switch pi's working directory to a linked worktree.",
@@ -141,10 +184,10 @@ const gitWorktreeSwitchTool = defineTool({
 				isError: true,
 			};
 		},
-});
+	}));
 
 	/** Remove a linked worktree. */
-const gitWorktreeRemoveTool = defineTool({
+	pi.registerTool(defineTool({
 		name: "git_worktree_remove",
 		label: "Git Worktree Remove",
 		description: "Remove a linked worktree.",
@@ -155,16 +198,7 @@ const gitWorktreeRemoveTool = defineTool({
 				isError: true,
 			};
 		},
-});
+	}));
-
-// ─── Extension Entry Point ────────────────────────────────────────
-
-export default function (pi: ExtensionAPI) {
-	// Register tools
-	pi.registerTool(gitWorktreeCreateTool);
-	pi.registerTool(gitWorktreeListTool);
-	pi.registerTool(gitWorktreeSwitchTool);
-	pi.registerTool(gitWorktreeRemoveTool);
 
 	// Register /worktree command
 	pi.registerCommand("worktree", {