fix(tools): make DaemonThreadPoolExecutor compatible with Python 3.14

[Ufonik88]

Summary

DaemonThreadPoolExecutor._adjust_thread_count (used for parallel tool execution and subagent timeout wrappers) reads self._initializer / self._initargs directly. Python 3.14 refactored concurrent.futures.thread: ThreadPoolExecutor.__init__ no longer stores those attributes — the initializer now lives in a WorkerContext produced by _create_worker_context(), and _worker's signature became (executor_reference, ctx, work_queue).

On 3.14 every concurrent tool batch fails at the first worker spawn:

AttributeError: 'DaemonThreadPoolExecutor' object has no attribute '_initializer'

This breaks any parallel tool batch (skill_view/search_files/read_file/patch fan-out, cron job runs, subagent submit) on interpreters where the venv resolved to Python 3.14.

Root cause

tools/daemon_pool.py, _adjust_thread_count — worker args tuple hard-coded self._initializer, self._initargs, which only exist on Python ≤3.13.

Fix

Route worker args through a new _daemon_worker_args() helper that adapts to the running interpreter:

• 3.14+: build the WorkerContext via executor._create_worker_context() and pass (weakref, ctx, work_queue).
• 3.8–3.13: keep the legacy (weakref, work_queue, initializer, initargs) tuple, using getattr so missing attrs degrade safely.

All call sites (tools/async_delegation.py, tools/skills_hub.py, tools/delegate_tool.py) share the one fixed class, so the whole bug class is covered.

Verification

• tests/tools/test_daemon_pool.py — 3 passed on Python 3.14.4 (the existing tests exercise worker spawn, which is exactly the failing path).
• Manual: submit batches with and without an initializer/initargs on 3.14.4 — results correct, initializer runs once per worker.
• Live repro: parallel tool batches in the running gateway failed with the AttributeError before the fix and complete normally after.

[alt-glitch]

This was generated by AI during triage.

Duplicate of #65182: both implement the same Python 3.14 WorkerContext/_worker compatibility repair in tools/daemon_pool.py. #65182 is the earlier open implementation.