Fix full CI argument comments and cross targets

[andrei-hasna]

Summary

• Adds exact argument-comment lint annotations for the inherited Linux full-matrix failures from main run 29637765162.
• Installs required cross Rust targets explicitly in full CI lint/build and reusable nextest archive/shard jobs for:
  • x86_64-unknown-linux-musl
  • aarch64-unknown-linux-musl
  • aarch64-pc-windows-msvc
• Preserves native lanes and does not skip, weaken, or bypass any matrix gate.

CI failure classification

Current main full-CI run 29637765162 at a0ee6df:

• Argument comment lint - Linux: real source lint class; job aborted with 69 argument-comment violations. This PR applies mechanical /*param*/ annotations only.
• Cross-target install class: real workflow/toolchain setup class; E0463: can't find crate for core with notes that the target may not be installed / rustup target add ... for:
  • Lint/Build — ubuntu-24.04 - x86_64-unknown-linux-musl
  • Lint/Build — ubuntu-24.04 - x86_64-unknown-linux-musl (release)
  • Lint/Build — ubuntu-24.04-arm - aarch64-unknown-linux-musl
  • Lint/Build — ubuntu-24.04-arm - aarch64-unknown-linux-musl (release)
  • Lint/Build — windows-latest - aarch64-pc-windows-msvc
  • Lint/Build — windows-latest - aarch64-pc-windows-msvc (release)
  • Tests — windows-11-arm - aarch64-pc-windows-msvc / Build nextest archive
• Tests — windows-11-arm - aarch64-pc-windows-msvc / Platform result: secondary aggregation failure caused by the Windows ARM archive/shard failure.
• Additional real class observed while the run continued: macOS aarch64 test failures in shards 1/4 through 4/4. Representative failures include background-agent tests assuming /bin/true exists on macOS, shared managed-worktree rejection expecting an error but receiving a queued agent, worktree reconciliation assertion failure, and a TUI command_popup_app snapshot mismatch. This PR reports but does not remediate that separate test class.
• Some ubuntu/windows test jobs were still in progress when this PR body was updated; those are not classified as failed here until GitHub marks them failed.

Prior full-CI run 29538027986 at 79b33b2:

• Same inherited Linux argument-comment lint class.
• Same missing cross Rust target class for x86_64/aarch64 musl and aarch64 Windows MSVC lint/build/archive jobs.
• Downstream platform-result failures followed failed archive/shard jobs.
• Extra prior ubuntu/macOS/windows shard failures inspected were DotSlash/setup/download transient/secondary failures in that run, not the same as the new macOS test failures observed in 29637765162.

Validation

• just fmt — PASS
• git diff --check — PASS
• YAML parse for .github/workflows/rust-ci-full.yml and .github/workflows/rust-ci-full-nextest-platform.yml — PASS
• actionlint 1.7.12 on touched workflow files — PASS
• just check-fast -p codex-core -p codex-app-server -p codex-api -p codex-exec -p codex-known-provider-models -p codex-state -p codex-tui — PASS
• just fix -p codex-core -p codex-app-server -p codex-api -p codex-exec -p codex-known-provider-models -p codex-state -p codex-tui — PASS
• Staged secret scan: gitleaks git --staged --redact --no-banner --no-color — PASS, no leaks found
• Range secret scan: gitleaks git --log-opts='a0ee6df908965b138853439e2a32c59d944450a8..HEAD' --redact --no-banner --no-color — PASS, no leaks found

Local lint constraint

• Exact just argument-comment-lint was attempted twice. It failed before reaching source lint execution because local Bazel analysis fails in external LLVM/libunwind setup: glob pattern 'include/**' didn't match anything for external/llvm++llvm_source+libunwind/BUILD.bazel.
• bazel clean --expunge did not resolve that local external-repository failure.
• Package/source Dylint fallbacks were also attempted for the touched crates and failed before linting because the wrapper uses nightly-2025-09-18 / rustc 1.92.0-nightly, while current dependencies require newer Rust (sqlx requires 1.94, constant_time_eq requires 1.95).