fix(review): surface zero reviewer coverage (#7783)

[atomantic]

Summary

• distinguish zero reviewer coverage from a clean review when every configured reviewer has a configuration fault
• persist real reviewer configuration faults, clear them after a successful review, and surface them in health details and Code Reviewers settings
• document the run-summary state across local-review prompts and preserve prompt-version integrity

Verification

• focused server suites: 283 passed
• focused route suites: 56 passed
• focused client suites: 102 passed
• pregate: client lint and 22 selected server guard suites, 219 tests passed

The configured OpenCode reviewer is optional (~opt) and was unavailable because its API could not be reached; focused self-review, tests, and pregate are complete, so this does not block publication or merge under the configured policy.

Closes #7783

[atomantic]

Required CI is red on the current head: the server suite's import-budget guard reports 116,547 static module instantiations against the 116,500 cap. A clean checkout of the current origin/main reports the same pre-existing failure, so this is not caused by #7783; the PR remains open for the baseline gate to be repaired before merge.