CI: Refine workflow for performance/reliability

[jserv]

This improves CI pipeline with toolchain caching, parallel builds, and error handling. It separates lint job to avoid duplication across matrix builds, adding concurrency control, job timeouts, and least-privilege permissions.

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Summary by cubic

Refined CI to run faster and fail safer with separate linting, cached toolchains, and parallel matrix builds. Adds cancel-in-progress, strict timeouts, and least-privilege permissions, plus more robust test summarization.

• Refactors
  • Split out a fast lint job (clang-format/shfmt only) that gates matrix tests.
  • Cache the riscv toolchain per toolchain type; run GNU with full tests and LLVM as build-only.
  • Add workflow concurrency to cancel duplicate runs and set job timeouts.
  • Use least-privilege permissions and actions/checkout@v5.
  • Speed up builds with make -j and stricter error handling (set -euo pipefail).
  • Harden test summary: guard upload/comment if generated, clearer final status, and standardize semaphore results to "Overall: PASS" with criteria line (semaphore:overall=skipped).

^{Written for commit 26465ce. Summary will update automatically on new commits.}

[github-actions]

Linmo CI Test Results

Overall Status: ✅ passed
Timestamp: 2025-11-20T03:26:46+00:00

Toolchain Results

Toolchain	Build	Crash Test	Functional
GNU	✅ passed	✅ passed	✅ passed
LLVM	✅ passed	⏭️ skipped	⏭️ skipped

Application Tests

App	GNU	LLVM
cond	✅ passed	⏭️ skipped
coop	✅ passed	⏭️ skipped
cpubench	✅ passed	⏭️ skipped
echo	✅ passed	⏭️ skipped
hello	✅ passed	⏭️ skipped
mqueues	✅ passed	⏭️ skipped
mutex	✅ passed	⏭️ skipped
pipes	✅ passed	⏭️ skipped
pipes_small	✅ passed	⏭️ skipped
pipes_struct	✅ passed	⏭️ skipped
prodcons	✅ passed	⏭️ skipped
progress	✅ passed	⏭️ skipped
rtsched	✅ passed	⏭️ skipped
semaphore	✅ passed	⏭️ skipped
suspend	✅ passed	⏭️ skipped
test64	✅ passed	⏭️ skipped
test_libc	✅ passed	⏭️ skipped
timer	✅ passed	⏭️ skipped
timer_kill	✅ passed	⏭️ skipped

Functional Test Details

Test	GNU	LLVM
mutex:data_consistency	✅ passed	⏭️ skipped
mutex:fairness	✅ passed	⏭️ skipped
mutex:mutual_exclusion	✅ passed	⏭️ skipped
mutex:overall	✅ passed	⏭️ skipped
semaphore:overall	✅ passed	⏭️ skipped

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Report generated from test-summary.toml