fix(opencode): install system llvm tools for coverage sandbox

[seonghobae]

Summary

OpenCode coverage-evidence fails on Rust workspaces (observed on ContextualWisdomLab/TEPP#46 @ 835922c) with:

cargo llvm-cov --workspace --all-features --fail-under-lines 100 --show-missing-lines
error: failed to find llvm-tools-preview

Root cause: the trusted coverage Docker image installs apt cargo/rustc and a musl cargo-llvm-cov binary, but not rustup llvm-tools-preview. TEPP (and other repos) already declare the component in rust-toolchain.toml; apt rustc ignores that.

Fix

• Install Debian llvm in the coverage tool image
• Symlink llvm-cov / llvm-profdata into /usr/local/bin
• Set LLVM_COV / LLVM_PROFDATA image env
• Export the same tools from ensure_rust_toolchain when present

Test plan

• Merge this workflow change to main
• Re-dispatch OpenCode Review for TEPP#46 and confirm coverage-evidence no longer fails on llvm-tools-preview
• Confirm a non-Rust repo coverage image still builds

Summary by CodeRabbit

• 개선 사항
  • 코드 커버리지 측정 환경을 안정화했습니다.
  • 커버리지 실행 시 필요한 LLVM 도구를 자동으로 인식하고 사용하도록 개선했습니다.
  • 신뢰된 커버리지 환경에서 도구 경로가 일관되게 설정되어 측정 결과의 재현성이 향상되었습니다.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: d8f86b90-958f-459a-bc5f-ae16d56e033c

📥 Commits

Reviewing files that changed from the base of the PR and between c47afc2 and e69a81e.

📒 Files selected for processing (1)

• .github/workflows/opencode-review-dispatch.yml

Included review availability: Your plan includes up to 1 review per rolling hour; 0 remain after this review.

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📝 Walkthrough

Walkthrough

Coverage Docker 이미지에 LLVM 도구를 추가합니다. llvm-cov와 llvm-profdata를 표준 경로에 연결합니다. Rust coverage 실행 시 기존 설정이 없으면 시스템 LLVM 도구 경로를 사용합니다.

Changes

LLVM coverage 도구 설정

Layer / File(s)	Summary
LLVM 설치 및 경로 설정 .github/workflows/opencode-review-dispatch.yml	Coverage 이미지에 llvm을 설치합니다. llvm-cov와 llvm-profdata를 /usr/local/bin에 연결합니다. 기존 LLVM_COV 및 LLVM_PROFDATA 값이 없으면 시스템 도구 경로를 설정합니다.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to e69a8

This localized workflow change is merge-ready after normal checks and review; no actionable merge-blocking risk remains.

Possibly related PRs

• ContextualWisdomLab/.github#827: LLVM coverage 설정의 기존 경계를 확장하고 도구 경로 기본값을 추가합니다.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	제목은 coverage 샌드박스에 시스템 LLVM 도구를 설치하는 주요 변경 사항을 정확하고 간결하게 설명합니다.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/opencode-coverage-llvm-tools

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[seonghobae]

Superseded by #1081 (same llvm coverage-image fix). #1069 OpenCode concurrency group was held by a non-cancellable hung model-pool job; v2 uses a new PR number.