v3.29.2: the strict row rule for the outfile import

The format is positional: an empty value drops its token, so the parser
now requires every data row to have exactly the header's column count.
That catches an empty value anywhere - including a middle one, which
would otherwise shift the following columns (a missing ADM made the KIC
columns read the KIK values: valid hex, wrong preset) - and a KICn/KIDn
pair declared in the header must carry a usable hex value in every row
(a placeholder fails).

A violation makes the whole file invalid: the report's error names the
line, no presets are returned, and an import (mode) answers 400 - it is
never partially imported.  The PWA disables the Import button while the
report carries an error and guards the call.

Unchanged per-row reports: a non-hex PIN/PUK/ADM/PSK value (dropped, the
card kept), an unsupported key size (that keyset skipped), a card whose
remaining keysets are unusable (skipped).  All three real samples satisfy
the rule exactly (11/11, 18/18, 18/18).

Docs: help EN/RU, api.md, the repo AGENTS.  Tests: the short/long row and
the placeholder-keyset file errors, the valid-file round trip, the
endpoint's refusal (nothing stored), the PWA's disabled button.
926 frontend + 945 Python; sw cache simple-v449.

tests/test_fetch_routes.py

@@ -966,6 +966,19 @@ class PresetStoreHttpTests(unittest.TestCase):
             'text': text, 'tars': [{'tar': '000000', 'msl': '16', 'keyset': 99}]})
         self.assertEqual(status, 400, resp)
         self.assertIn('keyset', resp['error'])
+        # an invalid file (a row with a missing value, v3.29.2): the preview
+        # shows the error, the import refuses it - never a partial import
+        bad = ('ICCID KIC1 KID1\n' + '8970119000004600098F 00112233445566778899AABBCCDDEEFF\n')
+        status, resp = self._post('/api/presets/import-outfile', {'text': bad})
+        self.assertEqual(status, 200, resp)
+        self.assertEqual(resp['presets'], [])
+        self.assertIn('the header declares 3 columns', resp['report']['error'])
+        before = len(self.store.list())
+        status, resp = self._post('/api/presets/import-outfile', {
+            'text': bad, 'mode': 'merge'})
+        self.assertEqual(status, 400, resp)
+        self.assertIn('the file is invalid', resp['error'])
+        self.assertEqual(len(self.store.list()), before)
         # a non-list TAR table is the caller's error, never a silent fallback
         status, resp = self._post('/api/presets/import-outfile', {
             'text': text, 'tars': 'nope'})