feat(HAI-034): use humanized worktree names instead of task-ID-based directories

- Add worktree-names module with adjective-animal name generator (generateWorktreeName)
- Update executor to assign humanized random worktree names and support dependency worktree reuse
- Remove task-ID fallback paths from merger and store; add shared worktree cleanup via findWorktreeUser
- Remove worktree pool module and related scheduler/integration tests
- Update dashboard worktree label tests and add JSDoc documentation for worktree naming

packages/engine/src/merger.ts

@@ -1,5 +1,4 @@
 import { execSync } from "node:child_process";
-import { join } from "node:path";
 import { existsSync } from "node:fs";
 import type { TaskStore, Task, MergeResult } from "@hai/core";
 import { createHaiAgent } from "./pi.js";
@@ -101,7 +100,7 @@ export async function aiMergeTask(
   }
 
   const branch = `hai/${taskId.toLowerCase()}`;
-  const worktreePath = task.worktree || join(rootDir, ".worktrees", taskId);
+  const worktreePath = task.worktree;
   const result: MergeResult = {
     task,
     branch,
@@ -110,6 +109,10 @@ export async function aiMergeTask(
     branchDeleted: false,
   };
 
+  if (!worktreePath) {
+    console.warn(`[merger] ${taskId}: no worktree path set — skipping worktree cleanup`);
+  }
+
   // 2. Check branch exists
   try {
     execSync(`git rev-parse --verify "${branch}"`, {
@@ -221,17 +224,23 @@ export async function aiMergeTask(
     session.dispose();
   }
 
-  // 7. Clean up worktree — release to pool if recycling is enabled
-  if (existsSync(worktreePath)) {
-    const settings = await store.getSettings();
-    if (options.pool && settings.recycleWorktrees) {
-      // Detach HEAD so the task branch can be deleted in step 8
-      try {
-        execSync("git checkout --detach", { cwd: worktreePath, stdio: "pipe" });
-      } catch { /* non-fatal — prepareForTask will reset HEAD on next acquire */ }
-      options.pool.release(worktreePath);
+  // 7. Delete branch (always per-task, regardless of worktree sharing)
+  try {
+    execSync(`git branch -d "${branch}"`, { cwd: rootDir, stdio: "pipe" });
+    result.branchDeleted = true;
+  } catch {
+    try {
+      execSync(`git branch -D "${branch}"`, { cwd: rootDir, stdio: "pipe" });
+      result.branchDeleted = true;
+    } catch { /* non-fatal */ }
+  }
+
+  // 8. Clean up worktree — only if no other non-done task still references it
+  if (worktreePath && existsSync(worktreePath)) {
+    const otherUser = await findWorktreeUser(store, worktreePath, taskId);
+    if (otherUser) {
+      console.log(`[merger] Worktree retained — still needed by ${otherUser}`);
       result.worktreeRemoved = false;
-      console.log(`[merger] Worktree returned to pool: ${worktreePath}`);
     } else {
       try {
         execSync(`git worktree remove "${worktreePath}" --force`, {
@@ -243,17 +252,6 @@ export async function aiMergeTask(
     }
   }
 
-  // 8. Delete branch
-  try {
-    execSync(`git branch -d "${branch}"`, { cwd: rootDir, stdio: "pipe" });
-    result.branchDeleted = true;
-  } catch {
-    try {
-      execSync(`git branch -D "${branch}"`, { cwd: rootDir, stdio: "pipe" });
-      result.branchDeleted = true;
-    } catch { /* non-fatal */ }
-  }
-
   // 9. Move task to done
   await completeTask(store, taskId, result);
   return result;