Cross-agent log search

[CodeBuildder]

Context

Unified log search across all four namespaces via the Sentinel shell. Parent: #46.

Acceptance Criteria

• Search bar queries Loki logs across sentinel-platform, phoenix, argus, sentinel namespaces
• Results returned within 5s for queries spanning 24h
• Log results annotated with agent source (argus/phoenix/sentinel/platform)
• Results link to the relevant incident or experiment record if one exists

Dependencies

Blocked by: none | Blocks: none

Notes

No model tier. Queries Loki.