feat(pin): exactly 4 digits, entered on the 4th digit

The keypad has no OK key; the 4th digit submits, so a tap that also
arrives as START can no longer submit a partial PIN (the likely cause
of "Wrong PIN" before the code opened). PINs set by earlier versions
still unlock and are then replaced by a 4-digit one. Opening an entry
ignores a second request from the same tap. A Require PIN sent from
the phone while the watch is locked now applies at the next PIN
instead of waiting for Confirm all. The linter skips .claude.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/tools/tests/test_gen_fixture_wrap.py b/tools/tests/test_gen_fixture_wrap.py
index 1c72e66..c7b11d5 100644
--- a/tools/tests/test_gen_fixture_wrap.py
+++ b/tools/tests/test_gen_fixture_wrap.py
@@ -31,3 +31,11 @@ def test_hkdf_matches_rfc5869_case_3() -> None:
 def test_generated_wrap_matches_the_fixture() -> None:
     assert gen_fixture_wrap.fixture_wrap().hex() == fixture_constant("FIXTURE_WRAP")
     assert gen_fixture_wrap.MASTER_KEY.hex() == fixture_constant("FIXTURE_MASTER_KEY")
+
+
+def test_fixture_pin_has_the_new_pin_length() -> None:
+    assert gen_fixture_wrap.PIN.decode() == fixture_constant("FIXTURE_PIN")
+    assert len(gen_fixture_wrap.PIN) == gen_fixture_wrap.PIN_DIGITS
+    key_manager = (ROOT / "source" / "storage" / "KeyManager.mc").read_text(encoding="utf-8")
+    assert f"static const PIN_DIGITS = {gen_fixture_wrap.PIN_DIGITS};" in key_manager
+    assert f'static const PIN_LENGTH_KEY = "{gen_fixture_wrap.PIN_LENGTH_KEY}";' in key_manager