Added plugin/add-on system

Plugins live in plugins/<name>/ with a manifest.json and a LabPlugin
subclass. Enabled/disabled in Settings > Plugins tab; state persists in
plugins/enabled.json and in .labdaq profiles (loading a profile
enables/disables plugins to match). Plugins can contribute toolbar
buttons, BaseDevice instances (auto-wired into acquisition pipeline),
custom signal filter classes, a settings widget, and profile state via
get_save_state/apply_save_state. Load errors now report the exact
failing stage (file not found, class missing, on_load crash).
Includes example plugin skeleton and docs/plugin-development.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/core/signal_processor.py b/core/signal_processor.py
index 417d142..723de66 100644
--- a/core/signal_processor.py
+++ b/core/signal_processor.py
@@ -185,6 +185,16 @@ def filter_from_dict(d: dict) -> FilterBase:
     return cls(**params)
 
 
+def register_filter_class(name: str, cls) -> None:
+    """Register a plugin-provided filter class by type name."""
+    FILTER_CLASSES[name] = cls
+
+
+def unregister_filter_class(name: str) -> None:
+    """Remove a previously registered plugin filter class."""
+    FILTER_CLASSES.pop(name, None)
+
+
 # ══════════════════════════════════════════════════════════════════════════════
 #  Derived channel definitions
 # ══════════════════════════════════════════════════════════════════════════════