fix(review): update offline Rust coverage toolchain

[seonghobae]

Evidence

The required OpenCode repository_dispatch run https://github.com/ContextualWisdomLab/.github/actions/runs/29676953842 evaluated ContextualWisdomLab/codec-carver#250 at current head 4ffe820524640c84f904d93900a735cd21e61375.

• Python: 561 collected, 486 passed, 75 skipped, 100% line coverage.
• Python docstrings: 100%.
• Rust: failed before test execution because the trusted coverage image installed Ubuntu Cargo 1.75.0 and could not parse edition = "2024".
• Exact failure: feature edition2024 is required and Cargo 1.75.0.

The target crate builds and passes its Rust tests with the current stable toolchain. This is a central evidence-toolchain compatibility defect, not an application test failure.

Scope

• Replace the stale distro Cargo/rustc pair in the trusted offline coverage image with a digest-pinned official Rust stable amd64 image.
• Keep all PR-controlled execution under the existing --network=none, tokenless, capability-restricted sandbox.
• Preserve the hash-pinned cargo-llvm-cov and Python requirements contracts.
• Add static regression assertions for the pinned Rust image, removal of distro Cargo/rustc, and current toolchain version evidence.

Acceptance criteria

• The central test suite, Ruff, workflow syntax, and git diff --check pass.
• A new current-head repository_dispatch run for ContextualWisdomLab/codec-carver#250 reaches Rust coverage rather than failing manifest parsing.
• Any subsequent Rust coverage gap is reported with exact missing-line evidence.
• The exact current-head OpenCode review is regenerated only after coverage evidence passes.

Agent: Codex
Recorded: 2026-07-19T15:58:00+09:00
Phase: Ops

Unblocks: ContextualWisdomLab/codec-carver#250

[seonghobae]

PR #592 is at current head 137ff8b.

Current evidence:

• Strix current-head run 29683525528: success.
• Required OpenCode repository_dispatch run 29683750497: coverage-evidence succeeded; the real-model review pool is still in progress.
• Local full suite: 634 passed.
• Official Python coverage contract: 5,527 statements, 0 missed, 100%.
• Interrogate: 514/514, 100%.
• Targeted OpenCode contract/model-pool tests: 54 passed.
• Ruff, Bash syntax, Actionlint expression/syntax checks, and git diff validation passed.

The PR now pins the official Rust 1.97.1 linux/amd64 image by exact manifest digest, seals rustup/cargo paths, installs llvm-tools-preview during the trusted networked image build, and preserves the existing tokenless network-disabled PR sandbox. It also caps central review-process candidates at 15 minutes with a one-hour pool budget so an unavailable provider cannot starve every fallback.

Acceptance remains open until PR #592 merges and a new exact-head review of codec-carver#250 reaches real Rust coverage.

[seonghobae]

Current-head retry 29683750497 reached successful coverage-evidence, then exhausted the real-model pool after about 183 minutes. Publish OpenCode review outcome failed with MODEL_OUTPUT_UNAVAILABLE; no review or comment was posted for head 137ff8b. Deterministic evidence correctly did not create an approval.

This is systemic rather than PR-local: among completed repository_dispatch OpenCode runs created after 2026-07-19T10:00:00Z, there were no successful runs; every completed run was failure or cancelled.

Live governance state:

• Ruleset 17921150 requires 2 approvals and last-push approval.
• bypass_actors is empty and current_user_can_bypass is never.
• The only repository collaborator is the PR author, so a human same-head approval is unavailable.
• No alternate default-branch manual workflow accepts a trusted review verdict or model/timeout override.

PR #592 remains fully validated locally and blocked only on external real-model reviewer availability. The safe next action requires provider recovery or explicit authority for a temporary governance change; neither is being assumed.