build: one list of checks, run by the release build and by CI alike

tools/check.sh is what build-release.sh ran before building — every
script's syntax, the manual, every tests/test-*.sh — moved, not copied,
so a new test is run by both with nothing else to edit. It now runs every
test even after one fails, keeps each one's output and a summary table
for a CI run, and with --base checks the change's hygiene too.

The manual's revision date honours SOURCE_DATE_EPOCH, so a release built
from a commit a day later ships the manual that commit holds.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

tools/build-manual

@@ -37,9 +37,10 @@ import argparse
 import base64
 import html
 import mimetypes
+import os
 import re
 import sys
-from datetime import date
+from datetime import date, datetime
 from pathlib import Path
 
 ROOT = Path(__file__).resolve().parent.parent
@@ -704,7 +705,13 @@ def main():
     if problems:
         return 1
 
-    revision = f"Revision {date.today():%d %B %Y}"
+    # The day the source was committed, when the build says so, rather than
+    # the day it was built: a release built from a commit a day later must
+    # still ship the manual that commit holds, or the build changes the
+    # tree it was built from. SOURCE_DATE_EPOCH is the usual name for it.
+    epoch = os.environ.get("SOURCE_DATE_EPOCH")
+    day = datetime.fromtimestamp(int(epoch)).date() if epoch else date.today()
+    revision = f"Revision {day:%d %B %Y}"
 
     if arguments.check:
         for name in ("classroom-manual.html", "classroom-manual.pdf"):