feat: animated-QR transfer, Android reader, relative-locktime preservation, karen7 hermetic tests

COMPATIBILITY.md

@@ -23,6 +23,25 @@ is updated to mark them as supported.
 See [`README.md`](README.md) for supported Electrum versions (currently 4.7.2
 and 4.8.0).
 
+## QR wire-format compatibility
+
+BAL exports/imports wills as QR codes. **BAL QR** (the default) is the plugin's
+own frame format and is only understood by BAL itself. The export page also
+supports **BC-UR v1**, **BC-UR v2** and **BBQR**:
+
+| Format    | Wire appearance            | Interop target                                       |
+|-----------|----------------------------|------------------------------------------------------|
+| BAL QR    | `BAL1<total><index><flag>…` (v2) / `BALQR1\|total\|index\|…` (legacy import-only) | Past/other BAL versions: **v2 exports are NOT readable by old builds**; old `BALQR1` exports still import here (default, best-of compression, flag `0` = plain, `Z` = deflate) |
+| BC-UR v1  | `ur:bytes/<bc32>`          | Blockchain Commons / Coldcard-style UR (BC32, SHA-256 digest, part counts per part) |
+| BC-UR v2  | `ur:bytes/<seq>-<seqlen>/<bytewords>` | BC-UR 2.x fountain codes (CBOR parts, CRC-32, bytewords-minimal) |
+| BBQR      | `B$<enc><type><N><n>…`     | Coinkite BitKit / Coldcard's BBQR animated-QR mode   |
+
+Import auto-detects the format of each scanned code; out-of-order, duplicate
+and (for UR v2) partially-lost fountain frames are handled. Interop is
+validation-tested against the reference C++ bc-ur encoder output and the
+BCR-2020-004/005 BC32 test vectors; it has not yet been cross-verified against
+third-party libraries (`ur`, `bbqr`, Coldcard firmwares).
+
 ## Reporting compatibility issues
 
 If you find a compatibility problem not listed here, please open an issue on