Utilize GitHub Actions for building and running via QEMU

[G36maid]

Implement GitHub Actions CI pipeline for testing Linmo across GNU and
LLVM RISC-V toolchains with automated reporting.

Features:

• Matrix testing for GNU and LLVM toolchains
• Automated app discovery and crash detection
• Functional test framework with criterion-based validation
• TOML-based result aggregation across toolchains
• Automated PR comments with detailed test results
• Proper failure handling and artifact collection

Components:

• .ci/ci-tools.sh: Unified tool for data collection, aggregation,
  and PR comment formatting
• .ci/run-app-tests.sh: Automated app testing with QEMU
• .ci/run-functional-tests.sh: Criterion-based functional tests
• .ci/setup-toolchain.sh: Automated toolchain installation
• .github/workflows/ci.yml: Complete CI workflow with summary job

The workflow ensures all tests run to completion, captures full output
for debugging, and fails CI based on the aggregated overall status

Fixes #2
Depend on #31

[jserv]

Rebase the latest main branch.

[jserv]

There should be only a commit, discarding unrelated ones.

[G36maid]

Rebase the latest main branch.

Already.

There should be only a commit, discarding unrelated ones.

Sure.

[jserv]

Carefully read https://cbea.ms/git-commit/ and strictly apply its rules when writing full sentences in commit messages.

[jserv]

Always rebase properly.

[G36maid]

Always rebase properly.

I'll make sure to rebase properly before merging. For now, I prefer to keep the commits.
Once everything is finalized, I'll squash or clean them up as needed.

[G36maid]

Do these results match what we wanted?
@jserv @Damien-Chen
Please check this run:
G36maid#6 (comment)

[cubic-dev-ai]

3 issues found across 6 files

Prompt for AI agents (all 3 issues)

Understand the root cause of the following 3 issues and fix them.


<file name=".ci/run-app-tests.sh">

<violation number="1" location=".ci/run-app-tests.sh:32">
A timeout (exit code 124 from `timeout`) indicates the QEMU run hung, but this branch treats it as a pass. That masks failures and lets broken apps appear healthy; only exit code 0 should be considered passing.</violation>
</file>

<file name="arch/riscv/build.mk">

<violation number="1" location="arch/riscv/build.mk:22">
The clang detection runs $(CROSS_COMPILE)gcc --version, but the LLVM toolchain only ships $(CROSS_COMPILE)clang, so CC_IS_CLANG never becomes 1 and the build selects the missing GNU binaries, breaking LLVM builds.</violation>
</file>

<file name=".ci/ci-tools.sh">

<violation number="1" location=".ci/ci-tools.sh:187">
The aggregated gnu apps section writes values like `app1=passed` without quotes, producing invalid TOML that downstream tools cannot parse.</violation>
</file>

_{React with 👍 or 👎 to teach cubic. Mention @cubic-dev-ai to give feedback, ask questions, or re-run the review.}

[cubic-dev-ai]

No issues found across 6 files

[jserv]

Rebase the latest main branch.

[jserv]

Thank @G36maid for contributing!