Update shared Gaia workflows and Sargo development tooling

Fix camera switching and Contacts/SMS activity routing across shared hosts.
Integrate Marketplace installation and native standalone recovery tools,
Bluetooth runtime packages and trusted certificates.

Update English/French READMEs and the shared changelog with tested scope
and remaining radio/audio/Bluetooth limitations. Preview17 remains the
existing APK; no new native image is released.

Validation: shared JavaScript and native Python tests; Android packaging
and payload parity from an isolated publication checkout.

tundra/tests/test_sparse_backup.py

@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: MPL-2.0
+import io
+from pathlib import Path
+import struct
+import sys
+import unittest
+sys.path.insert(0,str(Path(__file__).resolve().parents[1]/'tools'))
+from sparse_backup import receive
+
+
+def record(offset,data):return struct.pack('<QQ',offset,len(data))+data
+
+
+class BackupTests(unittest.TestCase):
+    def test_holes_and_final_size_are_restored(self):
+        stream=b'TUNRAW1\0'+record(2,b'abc')+record(9,b'x')+record(12,b'')
+        target=io.BytesIO();receive(io.BytesIO(stream),target,12)
+        # BytesIO does not extend on truncate; actual disk files do.
+        self.assertEqual(target.getvalue(),b'\0\0abc\0\0\0\0x')
+
+    def test_empty_disk_has_a_required_trailer(self):
+        receive(io.BytesIO(b'TUNRAW1\0'+record(100,b'')),io.BytesIO(),100)
+        with self.assertRaises(ValueError):receive(io.BytesIO(b'TUNRAW1\0'),io.BytesIO(),100)
+
+    def test_overlapping_or_out_of_bounds_blocks_rejected(self):
+        for records in (record(2,b'abc')+record(4,b'bad'),record(8,b'too long')):
+            with self.assertRaises(ValueError):receive(io.BytesIO(b'TUNRAW1\0'+records),io.BytesIO(),10)
+
+    def test_wrong_trailer_and_trailing_bytes_rejected(self):
+        for stream in (b'TUNRAW1\0'+record(9,b''),b'TUNRAW1\0'+record(10,b'')+b'extra'):
+            with self.assertRaises(ValueError):receive(io.BytesIO(stream),io.BytesIO(),10)
+
+    def test_truncated_payload_rejected(self):
+        with self.assertRaises(ValueError):receive(io.BytesIO(b'TUNRAW1\0'+struct.pack('<QQ',0,5)+b'four'),io.BytesIO(),10)
+
+
+if __name__=='__main__':unittest.main()