Add typo check with undo

The summary now has a Spelling line: "no typos found" or each fix listed by
slide ("fixed "OBEDIANCE" -> "OBEDIENCE""), with r to undo all or some.

- Uses macOS's own spelling checker and autocorrect via JXA, so it runs
  offline with nothing installed; ALL-CAPS emphasis words are checked too,
  and doubled small words ("the the") are removed
- Never changes names it doesn't know, Greek/Hebrew sermon words, or Bible
  compounds it would split (lampstand, firstfruits)
- An undone word goes into allowed-words.txt and is never changed again;
  undo re-runs the check from the text as it was before the fixes
- Tests: planted typos are fixed, all 18 real notes files are unchanged

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/run_tests.py

@@ -96,6 +96,22 @@ def main():
     check("only shared references reused (%d)" % len(shared), all(
         x.decode() in open(SERIES, "rb").read().decode("latin-1") for x in shared) and len(shared) <= 12)
 
+    # 6. typo check (macOS's spelling checker, so this needs a Mac): planted typos are fixed,
+    #    real notes are left alone
+    import spelling
+    try:
+        p = notes.parse(open(os.path.join(HERE, "typos", "Slides - Typo Test - Part 7.rtf"), "rb").read())
+        rep = spelling.check_and_fix(p, skip=set())
+        got = sorted((f.word, f.new) for f in rep.fixes)
+        want = sorted([("teh", "the"), ("the the", "the"), ("OBEDIANCE", "OBEDIENCE"), ("beleived", "believed")])
+        check("typos: planted typos fixed", got == want, "got %s" % got)
+        for f in sorted(os.listdir(NOTES)):
+            p = notes.parse(open(os.path.join(NOTES, f), "rb").read())
+            rep = spelling.check_and_fix(p)
+            check("typos: nothing changed in %s" % f, not rep.fixes, ", ".join("%s->%s" % (x.word, x.new) for x in rep.fixes))
+    except spelling.Unavailable as e:
+        print("skip   typo checks (%s)" % e)
+
     print()
     print("FAILED: %s" % failures if failures else "all checks passed")
     return 1 if failures else 0