Check staged docs for date footers; say what precheck skips

.claude/CLAUDE.md

@@ -12,7 +12,7 @@ It holds policy and pointers only; facts live in the linked docs, and `./mfc.sh
     * Load a compiler and MPI before building. On a supported cluster, `source ./mfc.sh load -c <computer> -m <g|c>` loads a known-working module set. Pass both flags; omitting either waits for interactive input. Computer slugs are the first column of `toolchain/modules`; elsewhere, `module load` the equivalents
     * Agent shell tools run each command in a fresh shell, so a one-off `module load` or `source ./mfc.sh load` is gone by the next command. Chain it (`source ./mfc.sh load -c p -m g && ./mfc.sh build -j 8`) or put the steps in a script
     * Running mfc.sh commands can create a lock file in build/ that is sticky, be careful (`toolchain/mfc/lock.py`)
-    * Run `./mfc.sh precheck` before pushing; it runs the same lint gate as CI
+    * Run `./mfc.sh precheck` before pushing; it runs the CI lint gate except the slow rendering and Fortran-compile unit tests
     * Iterate small: `./mfc.sh build -t simulation` builds one target; `./mfc.sh test --only <UUID>` runs one test; `./mfc.sh test --select-enforce` runs only the tests whose coverage touches your changed files
 * Programming and Design:
     * New code should follow the DRY principle and also make side-effect code DRY as well

docs/documentation/contributing.md

@@ -802,7 +802,7 @@ Every push to a PR triggers CI. Understanding the pipeline helps you fix failure
 
 ### Lint Gate (runs first, blocks the build and test jobs)
 
-All six checks must pass before any builds start (`./mfc.sh precheck` runs them locally, plus example-case validation):
+All six checks must pass before any builds start. `./mfc.sh precheck` runs them locally, plus example-case validation, but skips the slow rendering and Fortran-compile unit tests in the toolchain lint:
 
 1. **Formatting** — `./mfc.sh format` must leave no diff
 2. **Spelling** — `./mfc.sh spelling`

toolchain/mfc/lint_docs.py

@@ -847,13 +847,22 @@ def check_module_categories(repo_root: Path) -> list[str]:
 
 
 def check_page_date_footers(repo_root: Path) -> list[str]:
-    """Check that no doc carries a committed last-updated footer (docs/inject-dates.py adds it at build time)."""
-    doc_dir = repo_root / "docs" / "documentation"
+    """Check that no tracked doc is staged with a last-updated footer (docs/inject-dates.py adds it at build time).
+
+    Reads the index, not the working tree: a local docs build writes footers into every page, and only a staged one
+    would freeze its date.
+    """
+    import subprocess
+
+    try:
+        tracked = subprocess.run(["git", "ls-files", "docs/documentation/*.md"], capture_output=True, text=True, cwd=repo_root, check=True).stdout.split()
+    except (FileNotFoundError, subprocess.CalledProcessError):
+        return []
     errors = []
-    for md_file in sorted(doc_dir.glob("*.md")):
-        if "Page last updated:" in md_file.read_text(encoding="utf-8"):
-            rel = md_file.relative_to(repo_root)
-            errors.append(f"  {rel} contains a 'Page last updated' footer, which freezes its date. Fix: remove it (the docs build adds it from git history)")
+    for rel in tracked:
+        staged = subprocess.run(["git", "show", f":{rel}"], capture_output=True, text=True, cwd=repo_root, check=False).stdout
+        if "Page last updated:" in staged:
+            errors.append(f"  {rel} is staged with a 'Page last updated' footer, which freezes its date. Fix: drop the footer (the docs build adds it from git history)")
     return errors