fix(kanban): surface active PR respawn guards

[valentin-momboeuf]

Summary

• exclude active-PR guarded ready tasks from spawnable-ready telemetry
• surface respawn_guarded task/reason entries in dispatch JSON, CLI, daemon, and gateway logs
• document blocking review-required PR handoffs to avoid ready+active_pr limbo

Test Plan

• scripts/run_tests.sh tests/hermes_cli/test_kanban_db.py -k 'has_spawnable_ready or respawn_guard' -v
• scripts/run_tests.sh tests/hermes_cli/test_kanban_cli_dispatch_passthrough.py -v
• scripts/run_tests.sh tests/hermes_cli/test_kanban_db.py tests/hermes_cli/test_kanban_cli_dispatch_passthrough.py tests/hermes_cli/test_kanban_core_functionality.py -k 'kanban or gateway_dispatcher or dispatch'
• python3 -m compileall -q gateway/kanban_watchers.py hermes_cli/kanban.py hermes_cli/kanban_db.py

[valentin-momboeuf]

Local verification completed before opening this PR:

• python3 -m compileall -q gateway/kanban_watchers.py hermes_cli/kanban.py hermes_cli/kanban_db.py
• scripts/run_tests.sh tests/hermes_cli/test_kanban_db.py -k 'has_spawnable_ready or respawn_guard' -v → 21 passed
• scripts/run_tests.sh tests/hermes_cli/test_kanban_cli_dispatch_passthrough.py -v → 5 passed
• scripts/run_tests.sh tests/hermes_cli/test_kanban_db.py tests/hermes_cli/test_kanban_cli_dispatch_passthrough.py tests/hermes_cli/test_kanban_core_functionality.py -k 'kanban or gateway_dispatcher or dispatch' → 398 passed

I attempted to merge after review, but this account lacks direct merge / auto-merge permission on NousResearch/hermes-agent.

[valentin-momboeuf]

Closing/abandoning this PR per Valentin's instruction; this was opened against the wrong upstream for the current need.