fix: preserve report identity and quota resilience

[blisspixel]

Summary

• bind human-readable report directories to the complete stored job identity and keep trusted storage metadata authoritative
• make local report writes atomic, include campaign reports in listing, hide the internal metadata sidecar, and apply retention per report without deleting the campaign container
• make optional quota observations total over arbitrary JSON, finite and bounded, neutral when unmeasured, and unable to revive stale cache after a failed forced refresh
• align MCP circuit is_open reporting with its recovered half-open state
• update release metadata, changelog, supported surface, threat model, roadmap, package fixtures, and agent-plugin checksums for 2.50.6

Verification

• 252 affected storage, context-index, quota-routing, consult, and MCP property tests passed with 2 expected platform skips
• 164 final affected and release-facing tests passed with 2 expected platform skips
• the complete local unit run produced 11,653 passes and 20 expected skips; its sole shell-PATH entrypoint assertion passed through the repository uv run environment used by CI
• strict mypy passed across 158 source files
• Ruff lint and format checks, file-size checks, complexity and security ratchets, paid-API boundary checks, documentation consistency, and lock validation passed
• wheel and source archive content validation and Twine checks passed
• two agent-plugin builds were byte-identical, all packaged checksums matched, and contained plugin plus host-profile smoke checks passed
• no paid provider calls were made