feat: CAP compatibility test as its own operation + append-only imports (v3.6.48)

The import probe no longer lives in 'Install Package (.cap file)': a
diagnostic that can leave a LOADED-only package does not belong in the
operation meant to produce a working applet.  /api/ram-install no longer
takes probe_imports; the install form's probe fieldset is gone.

New RAM operation CAP compatibility test (POST /api/cap-compat): the
server runs the format check, INSTALL [for load] and the LOAD blocks only
up to the block that completes the Import component (_cap_import_end +
_cap_compat_blocks, computed from the load file and the C4 TLV framing),
then stops - no last-block flag, no INSTALL [for install], so nothing is
committed and nothing needs deleting.  The verdict (imports_ok,
boundary_block/total_blocks) states it covers the LOAD/import gate only;
the link gate stays the real install's business.  Verified on the real
RemMobileID CAP: the boundary is LOAD 1/64, 2/128, 3/240 for 240/120/64 B
blocks - exactly the blocks where the live cards rejected the load.

_probe_import_versions(load_file, overrides, additions) now supports
append-only synthetic imports: +AID=version appends a new entry, the
Import component's size field and the Directory's Import size are patched,
and existing entries keep their positions (constant-pool import indices
stay valid); an AID that is already imported becomes a version override.
This is the card-capability query ('does this card export package X at
>= Y?') without building a probe applet.

PWA: new op section (CAP file + analysis + the version list + block size),
ramCompatTest with inline results and ramCompatVerdict, ramProbeParse
understands +AID=version; help EN/RU documents the operation, the two-step
bisect and the gate scope.

sw cache simple-v321; tests: 538 Python / 686 Node.

tests/test_fetch_routes.py

@@ -157,5 +157,39 @@ class CardFreeGetTests(unittest.TestCase):
             self.assertNotIn(path, _CARD_FREE_GET)
 
 
+class CapCompatHttpTests(unittest.TestCase):
+    """POST /api/cap-compat exists (the CAP compatibility test, v3.6.48)."""
+
+    def setUp(self):
+        self.server = _build_http_server('127.0.0.1', 0, PysimHandler)
+        self.server.log_requests = False
+        self.server.app = None
+        self.server.sl = None
+        self.server.scc = None
+        threading.Thread(target=self.server.serve_forever, daemon=True).start()
+        self.port = self.server.server_address[1]
+
+    def tearDown(self):
+        self.server.shutdown()
+        self.server.server_close()
+
+    def _post(self, path, body):
+        req = urllib.request.Request(
+            'http://127.0.0.1:%d%s' % (self.port, path),
+            data=json.dumps(body).encode(),
+            headers={'Content-Type': 'application/json'}, method='POST')
+        try:
+            with urllib.request.urlopen(req, timeout=5) as res:
+                return res.status, json.loads(res.read() or b'{}')
+        except urllib.error.HTTPError as e:
+            return e.code, json.loads(e.read() or b'{}')
+
+    def test_cap_compat_route_exists(self):
+        # without a card session it answers 503 (route present), not 404
+        status, resp = self._post('/api/cap-compat', {'cap_hex': '00'})
+        self.assertEqual(status, 503, resp)
+        self.assertIn('error', resp)
+
+
 if __name__ == '__main__':
     unittest.main()