perf(ci): prebuilt actionlint, skip input for rust-quality, run-speed rules

.github/workflows/actionlint.yml

@@ -11,16 +11,39 @@ on:
     paths:
       - ".github/workflows/**"
 
+concurrency:
+  group: actionlint-${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
 jobs:
   actionlint:
     name: Lint workflows
     runs-on: ubuntu-latest
     timeout-minutes: 5
     permissions:
       contents: read
+    env:
+      # Bump both values together; the checksum is in the release's
+      # actionlint_<version>_checksums.txt.
+      ACTIONLINT_VERSION: 1.7.12
+      ACTIONLINT_SHA256: 8aca8db96f1b94770f1b0d72b6dddcb1ebb8123cb3712530b08cc387b349a3d8
     steps:
-      - name: Check out repository
+      - name: Check out workflows
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          sparse-checkout: .github
+
+      # The prebuilt release binary replaces the rhysd/actionlint Docker
+      # action, which rebuilt its image on every run. The runner image
+      # already provides shellcheck, which actionlint uses for `run:` scripts.
+      - name: Install actionlint
+        run: |
+          set -euo pipefail
+          archive="$RUNNER_TEMP/actionlint.tar.gz"
+          curl -fsSL --retry 3 -o "$archive" \
+            "https://github.com/rhysd/actionlint/releases/download/v${ACTIONLINT_VERSION}/actionlint_${ACTIONLINT_VERSION}_linux_amd64.tar.gz"
+          echo "${ACTIONLINT_SHA256}  ${archive}" | sha256sum --check --strict
+          tar -xzf "$archive" -C "$RUNNER_TEMP" actionlint
 
       - name: Run actionlint
-        uses: rhysd/actionlint@914e7df21a07ef503a81201c76d2b11c789d3fca # v1.7.12
+        run: '"$RUNNER_TEMP/actionlint" -color'

.github/workflows/rust-quality.yml

@@ -68,10 +68,16 @@ on:
         required: false
         type: boolean
         default: true
+      skip:
+        description: Skip the job, for a change that touches no code; a skipped job still reports its check name as passing
+        required: false
+        type: boolean
+        default: false
 
 jobs:
   rust-quality:
     name: Quality
+    if: ${{ !inputs.skip }}
     runs-on: ${{ inputs.runs-on }}
     timeout-minutes: ${{ inputs.timeout-minutes }}
     permissions:

docs/ci-platform.md

@@ -59,3 +59,43 @@ release.
 Rust quality cache policy follows `docs/rust-ci.md`: compatible jobs restore one
 stable family, only successful `main` quality runs save it, failed jobs do not
 save it, and release/tag workflows do not use the quality cache.
+
+## Run speed
+
+These rules keep a CI run short without removing a check.
+
+- **Cancel superseded pull request runs only.** Give the CI workflow
+  `concurrency.group: ci-${{ github.event.pull_request.number || github.sha }}`
+  and `cancel-in-progress: ${{ github.event_name == 'pull_request' }}`. A push
+  to `main` gets a unique group, so every `main` commit keeps a complete run;
+  the release gate depends on that. A workflow that also reacts to title or
+  label events adds a separate group suffix for them, so they cannot cancel a
+  running suite.
+- **Filter documentation-only changes inside the workflow, not with `on.paths`.**
+  A workflow skipped by `paths` or `paths-ignore` never reports its checks, and
+  a required check that never reports blocks the merge. A `changes` job built on
+  `dorny/paths-filter` with `predicate-quantifier: every` computes `code`;
+  callers pass `skip: ${{ needs.changes.outputs.code != 'true' }}` to
+  `rust-quality.yml` or put `if: needs.changes.outputs.code == 'true'` on their
+  own jobs. A skipped job reports its check name as skipped, which counts as
+  passing for a required check. The release gate accepts only `success`, so it
+  must never depend on a check that a release commit can skip: a release commit
+  changes `Cargo.toml`, which is code. A repository with no required check may
+  filter with `paths-ignore` instead.
+- **Do not chain jobs that exchange no data.** Drop a `needs` that only orders
+  jobs. Keep `needs` for artifacts and outputs, and for the aggregate job.
+- **Count jobs.** A free organization runs 20 jobs at once, and 5 of them on
+  macOS. A run that starts more jobs than that queues the rest, so merge many
+  small jobs into one job with a loop, or into a few shards.
+- **Put checks that do not depend on the operating system on Ubuntu.** Use macOS
+  and Windows only for installers, packaging, and platform runtime behavior.
+- **Prefer prebuilt tools.** Download a checksum-pinned release binary, or use an
+  install action that downloads one. Do not run `cargo install` or `go install`
+  in a job. `actionlint.yml` installs the release binary and verifies its
+  SHA-256.
+- **Keep `cargo test`.** `cargo nextest` was measured on the hosted runners and
+  was slower for opy-rs (52 s to 149 s) and athena (40 s to 65 s), because it
+  starts one process per test.
+- **Optimize a dependency that dominates a debug test.** A
+  `[profile.dev.package.<crate>]` `opt-level` entry costs one cached compile and
+  can remove minutes of test time; Wright sets one for `workshop-rs`.