Add self-scoped Centaur investigator

[fineas-bot]

Summary

• add centaur-investigator self as the default current-sandbox/current-thread debug path
• restrict broad centaur-investigator investigate/search-sessions to CENTAUR_INVESTIGATOR_OPERATOR_MODE=1
• gate raw vlogs query/fields/field-values/streams behind operator mode and point agents to the self-scoped investigator instead
• update the sandbox prompt so ordinary agents debug their own sandbox/thread, not global logs or unrelated sessions

Safety boundary

• Default scope is the current CENTAUR_THREAD_KEY/session context.
• Cross-thread investigation fails closed unless operator mode is explicitly enabled.
• Returned debug context avoids raw Slack text, message part content, session event payload bodies, and raw log rows.
• vlogs health remains available, but raw VictoriaLogs exploration is operator-only.

Validation

• PYTHONPATH=/Users/fin-sa/worktrees/centaur-safe-investigator:/Users/fin-sa/worktrees/centaur-safe-investigator/services/sandbox:/Users/fin-sa/worktrees/centaur-safe-investigator/tools/infra uv run --with pytest --with asyncpg --with httpx --with rich --with typer --with python-dotenv pytest --import-mode=importlib tools/infra/centaur_investigator/tests/test_client.py tools/infra/vlogs/tests/test_client.py tools/infra/vlogs/test_client.py services/sandbox/test_install_tool_shims.py -> 24 passed
• git diff --check
• uvx --from tools/infra/centaur_investigator centaur-investigator health
• uvx --from tools/infra/vlogs vlogs query level:error --limit 1 -> denied without operator mode

[fineas-bot]

Closing as intentionally retired by the upstream-first Centaur sync in #76/paradigmxyz#311, not as an upstream-provided replacement. This tool can run only after a sandbox is healthy enough to execute it, so it does not cover pre-start failures, dead/stuck sandboxes, fleet failures, or most image/deployment drift. Maintaining a second Python authorization and self-query surface is not justified for that limited coverage. If self-triage later proves useful, it should return as a sanitized principal-JWT diagnostic endpoint on the upstream architecture.