The SPI bridge remembers its channels across restarts

The radio library keeps its channel table in memory only, so every bridge
restart came up with no channels while MeshTerm's own mute settings
survived. Snapshot the table to channels.json after every set or clear,
the way contacts already were, and replay it at startup.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

scripts/uconsole/meshterm-spi-bridge

@@ -746,6 +746,68 @@ def _wire_contact_persistence(companion, log) -> None:
     log.info("contact persistence at %s", path)
 
 
+def _wire_channel_persistence(companion, log) -> None:
+    """Keep the node's channel table across bridge restarts.
+
+    The runtime's ChannelStore is memory-only, like its contacts: every restart
+    came up with no channels, and MeshTerm's Channels page was empty until each
+    one was added again. Reload the last snapshot at startup and re-snapshot
+    after every set or clear, which the frame server makes through
+    ``set_channel`` / ``remove_channel`` on the companion.
+    """
+    import json
+
+    store = getattr(companion, "channels", None)
+    if store is None or not hasattr(companion, "set_channel"):
+        log.warning("channel persistence not wired (no channel store)")
+        return
+
+    path = HOME / ".local" / "share" / APP_NAME / "channels.json"
+
+    def snapshot() -> list:
+        out = []
+        for idx in range(getattr(store, "max_channels", 40)):
+            ch = store.get(idx)
+            if ch is not None and ch.name:
+                out.append({"idx": idx, "name": ch.name, "secret": bytes(ch.secret).hex()})
+        return out
+
+    def save() -> None:
+        try:
+            path.parent.mkdir(parents=True, exist_ok=True)
+            tmp = path.with_name(path.name + ".tmp")
+            tmp.write_text(json.dumps(snapshot()))
+            tmp.replace(path)
+        except Exception as exc:
+            log.warning("could not save channels (%s)", exc)
+
+    if path.exists():
+        try:
+            restored = 0
+            for entry in json.loads(path.read_text()):
+                if entry.get("name"):
+                    companion.set_channel(
+                        int(entry["idx"]), entry["name"], bytes.fromhex(entry["secret"])
+                    )
+                    restored += 1
+            log.info("restored %d channel(s) from %s", restored, path)
+        except Exception as exc:
+            log.warning("could not restore channels (%s)", exc)
+
+    for name in ("set_channel", "remove_channel"):
+        orig = getattr(companion, name, None)
+        if orig is None:
+            continue
+
+        def wrapped(*args, _orig=orig, **kwargs):
+            result = _orig(*args, **kwargs)
+            save()
+            return result
+
+        setattr(companion, name, wrapped)
+    log.info("channel persistence at %s", path)
+
+
 def _wire_trace_push(rt: str, companion, server, log) -> None:
     """Forward over-the-air trace replies to the client as PUSH_CODE_TRACE_DATA.
 
@@ -1098,6 +1160,7 @@ def run_bridge(host: str, port: int, node_name: str) -> int:
         companion = CompanionRadio(radio, identity, node_name=node_name, radio_config=radio_config)
         await companion.start()
         _wire_contact_persistence(companion, log)
+        _wire_channel_persistence(companion, log)
         pub = companion.get_public_key()
         log.info("node identity %s… (hash 0x%02x, name %r)", pub.hex()[:16], pub[0], node_name)