feat!: mux-py on DongLoRa Protocol v2 with tag-aware dispatch

The 1.0 Python mux, mirroring the Rust donglora-mux 1.0 one-for-one and implementing the full §13 multi-client semantics on the DongLoRa Protocol v2 wire format.

* Structural rewrite. donglora_mux/{daemon,intercept,session,tagmap}.py replace the 601-line __init__.py monolith.

* Tag-aware dispatch. TagMapper with skip-zero allocation and per-client bulk drop on disconnect. Multiple clients can have commands in flight concurrently; the single-oneshot response slot is gone.

* Full §13.2 multi-client SET_CONFIG semantics. Tracks (client_id, modulation) lock owner and synthesizes OK(APPLIED/MINE), OK(ALREADY_MATCHED/OTHER), or OK(LOCKED_MISMATCH/OTHER).

* TX loopback fan-out (§13.4). On TX_DONE(TRANSMITTED) the mux synthesizes an RX frame with origin = LOCAL_LOOPBACK for every connected client except the transmitter.

* Async ERR(EFRAME) fan-out: tag-0 framing errors are broadcast to all clients.

* Per-client TX cache on ClientSession so the loopback fan-out does not need the sender to re-buffer.

* Socket and serial fcntl.flock to prevent multiple mux instances from fighting over the same dongle or socket path.

* 500 ms keepalive matching PROTOCOL.md §3.4 (2x margin on the 1 s inactivity timer), replacing the 5 s cadence from 0.x.

* Clean SIGINT / SIGTERM shutdown: per-client handler tasks are tracked and cancelled, so blocked reader.read() calls no longer pin the event loop open.

CHANGELOG.md

@@ -1,19 +1,66 @@
 # Changelog
 
-## Unreleased
+## 1.0.0 — 2026-04-21
+
+### Breaking
+
+- **Upgraded to the DongLoRa Protocol v2 wire format.** The 0.x line spoke the legacy
+  v0.1 protocol with hardcoded tag constants (`TAG_OK=4`, `TAG_ERROR=5`,
+  `CMD_TAG_SET_CONFIG=2`, …) that don't exist in v1.0. This release is
+  wire-incompatible with 0.x clients and firmware.
+- **Pins `donglora>=1.0.0`** and uses its `donglora.frame` /
+  `donglora.events` / `donglora.commands` modules as the wire-level
+  backbone. No more in-package reimplementation of the wire protocol.
+- **Structural rewrite** mirroring the Rust sibling
+  [`donglora-mux`](https://crates.io/crates/donglora-mux) one-to-one:
+  `donglora_mux/{daemon,intercept,session,tagmap}.py` replace the single
+  601-line `__init__.py`.
 
 ### Added
 
-- Keepalive ping: detects unresponsive dongles (e.g. UART boards behind a
-  CP2102 bridge where the serial port stays open across ESP32 resets). Pings
-  every 5 seconds of idle, declares dongle lost after 2-second timeout.
-- Radio state restoration after reconnect: saved SetConfig and StartRx are
-  re-sent to the dongle so clients don't need to know a reset happened.
+- **`TagMapper`** — per-command device-tag allocator. Enables concurrent
+  out-of-order command/response correlation for multi-client setups
+  (the v0.1-era single-oneshot-response slot is gone).
+- **Full `§13.2` multi-client `SET_CONFIG` semantics** — tracks the
+  `(client_id, modulation)` lock owner. Cross-client calls synthesize:
+  - `OK(APPLIED / MINE, params)` when the caller owns the lock
+    (forwarded to dongle).
+  - `OK(ALREADY_MATCHED / OTHER, current)` when another client holds
+    the lock and the requested params byte-match.
+  - `OK(LOCKED_MISMATCH / OTHER, current)` when they differ; `current`
+    echoes the lock owner's actual modulation.
+  - Lock auto-releases when the owning client disconnects.
+- **TX loopback fan-out (`§13.4`)** — on `TX_DONE(TRANSMITTED)` the mux
+  synthesizes an `RX` frame with `origin = LOCAL_LOOPBACK` and sends it
+  to every connected client except the transmitter.
+- **Async `ERR(EFRAME)` fan-out** — if the dongle emits async framing
+  errors (tag 0), they're broadcast to all clients rather than swallowed.
+- **Per-client TX cache** on `ClientSession` so the loopback fan-out
+  doesn't need the sender to re-buffer the payload.
+- **Socket and serial file locking** (`fcntl.flock`) to prevent multiple
+  mux instances from fighting over the same dongle or socket path.
+- **500 ms keepalive** matching `PROTOCOL.md §3.4` (2× margin on the
+  1 s inactivity timer). Replaces the 5 s cadence from 0.x.
+- **Clean ^C / SIGTERM shutdown** — per-client handler tasks are tracked
+  and cancelled on shutdown, so blocked `reader.read()` calls no longer
+  pin the event loop open.
 
-### Fixed
+### Removed
 
-- Serial port opened without baud rate (defaulted to 9600 instead of 115200),
-  preventing connection to UART boards behind CP2102 bridges.
+- Every v0.1 wire constant and the inline `cobs` + raw `serial.Serial`
+  frame codec.
+- The single `pending_response: asyncio.Future` slot (fundamentally
+  incompatible with v1.0's per-tag concurrency).
+
+### Test coverage
+
+- 28 tests (up from 11):
+  - `test_tagmap.py` (6) — tag allocator behaviour.
+  - `test_intercept.py` (13) — every branch of the `decide()` matrix,
+    including the `ALREADY_MATCHED` / `LOCKED_MISMATCH` synthesis paths.
+  - `test_multiclient.py` (9) — asyncio-driven daemon dispatch tests:
+    concurrent tag routing, `SET_CONFIG` lock installation, TX loopback
+    to peer clients, lock release on disconnect, unsolicited-frame drop.
 
 ## 0.2.0 — 2026-04-08