feat: let workers claim jobs by intent

[pilipilisbot]

Summary

• add optional work-intent filtering to durable queue claims
• wire executor workers to the filter with a new gab run --work-intent flag
• cover filtered claims, same-work-key protection, and CLI intent parsing

Closes #158

Tests

• python -m pytest tests/test_queue.py tests/test_manual_enqueue_cli.py -q -> 28 passed
• full isolated suite with dashboard/web-push env cleared -> 315 passed, 1 warning

[ecarreras]

@pilipilisbot joder has mergejat sense dir res, no has fet documentació operativa, com funciona? no he pogut ni revisar els canvis!

La idea és que ho documentis perquè l'agent es pugui autoconfigurar segons el que digui el seu administrador

[pilipilisbot]

Follow-up opened: #160

What I added there:

• operational docs for intent-specific executor pools (review_only, work_allowed, and general/all)
• systemd/env support via GITHUB_AGENT_BRIDGE_WORK_INTENT, so an admin can configure worker specialization from the private env file instead of rewriting the unit
• policy-reference clarification that executor filters only affect queue claiming; they do not reclassify jobs, grant write permission, or change the prompt

Commit: 4475616 docs: explain intent-specific worker pools

Validation:

• ../github-agent-bridge-issue158/.venv/bin/python -m pytest tests/test_manual_enqueue_cli.py tests/test_queue.py -q -> 28 passed
• parser smoke test for all and comma-separated intents -> passed