[codex] Recheck skill state before serving guidance

[pmbstyle]

What changed

• refresh the current skill record inside _run_skill(...) before serving guidance
• reject dynamic skill_<id> calls when the skill was disabled or removed after tool registration
• add a regression test covering the stale-handler-after-disable path

Why

Recent skill management commits added enable/disable support, but dynamic skill handlers still captured the old skill record at registration time. That let a previously exposed skill_<id> tool keep returning guidance even after set_skill_enabled(..., enabled=False).

Impact

Disabled skills now stay disabled consistently for both generic use_skill and already-registered dynamic skill_<id> tools.

Validation

• PYTHONPYCACHEPREFIX=/tmp/pycache python3 -m py_compile src/octopal/tools/skills/management.py tests/test_skill_management.py
• git diff --check

Notes

Full pytest was not run here because the local system python3 environment does not have pytest installed.