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>

2 files changed, 58 insertions, 18 deletions

diff --git a/core/profile.py b/core/profile.py
index d21bf2f..fdd3a48 100644
--- a/core/profile.py
+++ b/core/profile.py
@@ -67,15 +67,19 @@ class ProfileDerived:
 
 @dataclass
 class Profile:
-    name:       str   = "Untitled Profile"
-    version:    str   = "1.0"
-    devices:    List[Dict]                   = field(default_factory=list)
-    controls:   List[Dict]                   = field(default_factory=list)
-    channels:   List[Dict]                   = field(default_factory=list)
-    pipelines:  List[Dict]                   = field(default_factory=list)
-    derived:    List[Dict]                   = field(default_factory=list)
-    plot:       Optional[Dict]               = None   # LayoutConfig.to_json()
-    settings:   Dict[str, Any]               = field(default_factory=dict)
+    name:         str   = "Untitled Profile"
+    version:      str   = "1.0"
+    devices:      List[Dict]                   = field(default_factory=list)
+    controls:     List[Dict]                   = field(default_factory=list)
+    channels:     List[Dict]                   = field(default_factory=list)
+    pipelines:    List[Dict]                   = field(default_factory=list)
+    derived:      List[Dict]                   = field(default_factory=list)
+    plot:         Optional[Dict]               = None   # LayoutConfig.to_json()
+    settings:     Dict[str, Any]               = field(default_factory=dict)
+    plugin_state:   Dict[str, Any]             = field(default_factory=dict)
+    # plugin_state = {plugin_id: plugin.get_save_state()}
+    plugins_enabled: List[str]                 = field(default_factory=list)
+    # plugins_enabled = [plugin_id, ...]  — which plugins were on when saved
 
     def to_json(self) -> str:
         return json.dumps(asdict(self), indent=2)
@@ -84,15 +88,17 @@ class Profile:
     def from_json(s: str) -> "Profile":
         d = json.loads(s)
         return Profile(
-            name      = d.get("name", ""),
-            version   = d.get("version", "1.0"),
-            devices   = d.get("devices", []),
-            controls  = d.get("controls", []),
-            channels  = d.get("channels", []),
-            pipelines = d.get("pipelines", []),
-            derived   = d.get("derived", []),
-            plot      = d.get("plot"),
-            settings  = d.get("settings", {}),
+            name         = d.get("name", ""),
+            version      = d.get("version", "1.0"),
+            devices      = d.get("devices", []),
+            controls     = d.get("controls", []),
+            channels     = d.get("channels", []),
+            pipelines    = d.get("pipelines", []),
+            derived      = d.get("derived", []),
+            plot         = d.get("plot"),
+            settings        = d.get("settings", {}),
+            plugin_state    = d.get("plugin_state", {}),
+            plugins_enabled = d.get("plugins_enabled", []),
         )
 
     def save(self, path: str):
@@ -135,6 +141,7 @@ class ProfileManager:
         control_specs: List,
         settings: dict,
         profile_name: str = "Profile",
+        plugin_manager=None,
     ) -> Profile:
         p = Profile(name=profile_name)
 
@@ -193,6 +200,18 @@ class ProfileManager:
                 pass
 
         p.settings = dict(settings)
+
+        # Plugin state + enabled list
+        if plugin_manager is not None:
+            p.plugins_enabled = plugin_manager.get_enabled_ids()
+            for plugin in plugin_manager.get_loaded():
+                try:
+                    state = plugin.get_save_state()
+                    if state:
+                        p.plugin_state[plugin.plugin_id] = state
+                except Exception:
+                    pass
+
         return p
 
     # ── Apply ─────────────────────────────────────────────────────────────────
@@ -205,6 +224,7 @@ class ProfileManager:
         control_panel,
         settings_ref: dict,
         engine=None,
+        plugin_manager=None,
     ):
         """Apply a loaded profile to the live application state."""
         from ui.control_editor import ControlSpec
@@ -329,4 +349,14 @@ class ProfileManager:
             except Exception as e:
                 print(f"[Profile] Could not restore plot layout: {e}")
 
+        # Plugin state
+        if plugin_manager is not None and profile.plugin_state:
+            for plugin_id, state in profile.plugin_state.items():
+                plugin = plugin_manager.get_plugin(plugin_id)
+                if plugin is not None:
+                    try:
+                        plugin.apply_save_state(state)
+                    except Exception as e:
+                        print(f"[Profile] Plugin '{plugin_id}' state restore error: {e}")
+
         return plot_cfg   # caller applies this to the chart
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
 # ══════════════════════════════════════════════════════════════════════════════