config: filter unknown toml keys before dataclass init

Prevents opaque TypeError on typos in config.toml; unknown
keys are logged as warnings and silently dropped.

src/tuimble/config.py

@@ -1,8 +1,12 @@
 """Configuration management."""
 
+import dataclasses
+import logging
 from dataclasses import dataclass, field
 from pathlib import Path
 
+log = logging.getLogger(__name__)
+
 CONFIG_DIR = Path.home() / ".config" / "tuimble"
 CONFIG_FILE = CONFIG_DIR / "config.toml"
 
@@ -60,9 +64,18 @@ def load_config(path: Path | None = None) -> Config:
 
     cfg = Config()
     if "server" in data:
-        cfg.server = ServerConfig(**data["server"])
+        cfg.server = _load_section(ServerConfig, data["server"])
     if "audio" in data:
-        cfg.audio = AudioConfig(**data["audio"])
+        cfg.audio = _load_section(AudioConfig, data["audio"])
     if "ptt" in data:
-        cfg.ptt = PttConfig(**data["ptt"])
+        cfg.ptt = _load_section(PttConfig, data["ptt"])
     return cfg
+
+
+def _load_section(cls, raw: dict):
+    """Instantiate a dataclass, silently dropping unknown keys."""
+    valid = {f.name for f in dataclasses.fields(cls)}
+    unknown = set(raw) - valid
+    if unknown:
+        log.warning("ignoring unknown config keys: %s", ", ".join(sorted(unknown)))
+    return cls(**{k: v for k, v in raw.items() if k in valid})