Propagate REPORTED state to nested observations

[Anionix]

Merged review finding:

• fix: close lifecycle terminal states #74 (comment)

The report transition currently updates only top-level manifest/results state. Per-format and per-claim/prompt observations remain BENCHMARKED even when packaged as reported evidence.

Acceptance:

• report transitions every BENCHMARKED format observation to REPORTED
• report transitions benchmarked claim and prompt observations to REPORTED
• FAILED and UNSUPPORTED observations remain terminal and unchanged
• rerendering an already reported run is idempotent
• focused tests cover fair, claims, and prompt result shapes