fix(tools): adapt DaemonThreadPoolExecutor for Python 3.14 _worker signature

[liuhao1024]

What does this PR do?

Fixes DaemonThreadPoolExecutor crash on Python 3.14 where _adjust_thread_count() references self._initializer and self._initargs, which no longer exist. Python 3.14 changed concurrent.futures.thread._worker from 4 params to 3, replacing (initializer, initargs) with a WorkerContext object created via self._create_worker_context().

Related Issue

Fixes #58596

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• tools/daemon_pool.py: Detect _worker signature at import time (inspect.signature, 3 vs 4 params) and branch _adjust_thread_count args accordingly. Python ≥3.14 passes self._create_worker_context() as the ctx argument; ≤3.13 passes self._initializer/self._initargs.
• tests/tools/test_daemon_pool.py: Added test_worker_signature_detection_matches_runtime (verifies _WORKER_USES_CTX matches runtime _worker param count) and test_concurrent_submit_with_context_path (10 concurrent submits under the ctx-based path).

How to Test

1. Run python -m pytest tests/tools/test_daemon_pool.py -v — all 6 tests should pass
2. On Python 3.14: python -c "from tools.daemon_pool import DaemonThreadPoolExecutor; e = DaemonThreadPoolExecutor(max_workers=1); print(e.submit(lambda: 42).result())" should print 42 (previously crashed with AttributeError)
3. On Python ≤3.13: same tests pass via the legacy 4-param _worker path

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/tools/test_daemon_pool.py -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: macOS 26, Python 3.14.0

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — N/A (stdlib change is cross-platform)
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

[alt-glitch]

This was generated by AI during triage.

Duplicate of #57459 — both PRs fix the same crash in tools/daemon_pool.py _adjust_thread_count (Python 3.14 removed _initializer/_initargs and changed _worker from 4 to 3 params). #57459 (created 2026-07-03, earlier) is canonical; it uses a getattr fallback, this PR uses an inspect.signature branch — same code-site, same goal, so the mechanism difference doesn't make this a separate fix.

Related: #58596 (the issue), #50077 / #47634 (same 3.14 theme but a different file, tools/async_delegation.py).

[liuhao1024]

Closing as a self-duplicate of #57459 — both fix the same DaemonThreadPoolExecutor crash on Python 3.14 (_initializer/_initargs removed). #57459 uses getattr fallback (simpler, already open since 2026-07-03); this PR uses inspect.signature branching (more thorough but same fix site). The getattr approach is sufficient since the fallback to None matches CPython's new behavior.