Add RISC-V CI test coverage

[liuq19]

Summary

• Add a stable CI job for riscv64gc-unknown-linux-gnu.
• Use taiki-e/setup-cross-toolchain-action with the qemu-user runner so cargo test --verbose executes under RISC-V emulation.

Validation

• rustup +stable target add riscv64gc-unknown-linux-gnu
• cargo +stable check --target riscv64gc-unknown-linux-gnu --all-targets
• python3 -c 'import yaml; yaml.safe_load(open(".github/workflows/ci.yml")); print("ok")'
• git diff --check

Note: the local cross-compile check emitted host CPU feature warnings from this machine's compiler flags when targeting RISC-V, but completed successfully.

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 71.16%. Comparing base (03545a9) to head (1aa7261).

Files with missing lines	Patch %	Lines
src/lazyvalue/value.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #229   +/-   ##
=======================================
  Coverage   71.16%   71.16%           
=======================================
  Files          42       42           
  Lines        9762     9762           
=======================================
  Hits         6947     6947           
  Misses       2815     2815           

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[Copilot]

Pull request overview

Adds CI coverage intended to run the test suite on RISC-V (riscv64gc-unknown-linux-gnu) under QEMU emulation, alongside a couple of small Rust cleanups.

Changes:

• Add a new GitHub Actions job for stable RISC-V testing using taiki-e/setup-cross-toolchain-action with qemu-user.
• Minor parser token-matching refactors to use byte-string literals for token arrays.
• Small cleanup in LazyValue’s Debug formatting.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/parser.rs	Refactors several token-array literals to byte-string equivalents for scanning/branching logic.
src/lazyvalue/value.rs	Simplifies a format_args! call in Debug output.
.github/workflows/ci.yml	Adds a new stable CI job intended to run tests under RISC-V emulation.

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