[Ravi Eda (ravimeda)]

Summary

This PR improves reliability of the Reviewer <--> Critic loop for ARM API reviews by
tightening protocol contracts and fallback behavior. The Critic was introduced in
#43494

What Changed

1. Added a non-empty response invariant for Critic dispatch: empty / "Agent
   completed with no output" returns are treated as host-side failures, retried up
   to 3 times with a reduced/compact-mode payload, then auto-fall back to
   critic-mode=unavailable.
2. Added compact-mode iteration support for iterations 2 and 3 (changed-findings +
   carry-over verdicts), with session-SHA re-fetch pinning and file-drift
   (carry-over-stale) checks.
3. Replaced the rigid fenced-YAML Critic input schema with tolerant prose parsing
   and sensible defaults; simplified the graph-handling flag to Graphs: true|false
   and folded prior-iteration carryover inline into the report.
4. Removed the manual session-handoff fallback path in favor of automatic
   unavailable-mode disclosure after bounded retries (no user action required).
5. Shrank the non-overridable FAIL catalog to 6 reasons; downstream-CI and
   reconciliation FAILs are now overridable with justification.
6. Updated supporting documentation (graph reasoning, downstream-CI impact,
   reviewer/critic workflow).
7. Updated the evaluation suite: new critic-subagent-failure-auto-unavailable
   protocol-safety test, refreshed fast-path / suppressions-yaml / typespec-required
   evals, and a hardened run-evals.ps1 with infrastructure-only auto-retry.

Impact

1. Reduces false-pass outcomes from empty or malformed Critic returns.
2. Makes retry and fallback behavior deterministic and auditable, and removes a
   brittle manual-paste handoff step.
3. Improves consistency between protocol docs, templates, agent guidance, and the
   eval suite.

Scope

Agent protocol, documentation, and evaluation-suite (test tooling) updates only.
No REST API spec surface changes. No SDK generation changes.

[github-actions]

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[Ravi Eda (ravimeda)]

Thanks for the contribution, Sandip Shahane (@sandipsh)

[Ravi Eda (ravimeda)]

Suhas Rao (ARM) (@raosuhas) please could you take a look