fix: keep ship review retries inside one invocation

[yolo-jared]

Summary

• treat agent-applied pre-landing fixes as an internal ship retry loop instead of requiring a second user invocation
• generate and install the Codex payload with the GPT overlay, including global ~/.agents discovery
• migrate source checkouts out of Codex skill-discovery roots to prevent recursive or Claude-source skill loading
• add regression coverage for same-invocation continuation, GPT generation, global installs, and discovery migration

Verification

• focused host and generator suites: 484 pass, 0 fail
• new release-autonomy regressions: 5 pass, 0 fail
• official non-eval suite under isolated global Git config: 4,440 pass, 2 unrelated failures, 488 skip
  • benchmark auth-remediation wording
  • session-runner observability comment count
  • both failing test/source surfaces are unchanged from origin/main

The non-eval command excludes the repository's LLM and periodic E2E groups through its documented ignore list.

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