feat: implement contextual help system with searchable overlay

- Add '?' button in expert mode status bar that opens help overlay
- Search input with fuzzy search (same algorithm as command palette)
- 43 help articles covering major features (sensing links, Fresnel zones,
  detection quality, presence prediction, fall detection, etc.)
- Articles stored as static JSON (dashboard/help_articles.json)
- No server round-trip - loads articles client-side
- Category filter buttons for easy navigation
- Keyboard shortcut: Ctrl+? to open help overlay

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

.needle-predispatch-sha

@@ -1 +1 @@
-6812da8ccb1b0675133a2e545faee98e07559a87
+0485d746ba3001bad6ee9eabfe485db2771a9cf0

dashboard/js/help.js

@@ -42,7 +42,7 @@
      */
     async function loadArticles() {
         try {
-            const response = await fetch('/help_articles.json');
+            const response = await fetch('help_articles.json');
             if (!response.ok) {
                 throw new Error('Failed to load help articles');
             }
@@ -121,16 +121,16 @@
      * Add help button to expert mode header
      */
     function addHelpButton() {
-        // Look for expert mode header or status bar
-        const header = document.querySelector('.expert-header, .view-header, .toolbar, #status-bar');
-        if (!header) {
-            // Try again after a delay
-            setTimeout(addHelpButton, 1000);
+        // Check if button already exists
+        if (document.getElementById('help-button')) {
             return;
         }
 
-        // Check if button already exists
-        if (document.getElementById('help-button')) {
+        // Look for the status bar button container (margin-left:auto; gap:6px)
+        const buttonContainer = document.querySelector('#status-bar > div[style*="margin-left:auto"]');
+        if (!buttonContainer) {
+            // Try again after a delay
+            setTimeout(addHelpButton, 500);
             return;
         }
 
@@ -141,7 +141,13 @@
         helpBtn.title = 'Help & Documentation (Ctrl+?)';
         helpBtn.onclick = () => HelpOverlay.open();
 
-        header.appendChild(helpBtn);
+        // Insert before the last status-item (FPS counter)
+        const fpsItem = buttonContainer.parentElement.querySelector('.status-item:last-child');
+        if (fpsItem) {
+            buttonContainer.insertBefore(helpBtn, fpsItem);
+        } else {
+            buttonContainer.appendChild(helpBtn);
+        }
     }
 
     /**

mothership/internal/db/migrations.go

@@ -78,6 +78,11 @@ func AllMigrations() []Migration {
 			Description: "add id, delivered, acknowledged columns to briefings table",
 			Up:          migration_014_add_briefing_delivery_columns,
 		},
+		{
+			Version:     15,
+			Description: "add feature_notifications table for feature discovery",
+			Up:          migration_015_add_feature_notifications,
+		},
 	}
 }
 
@@ -705,3 +710,17 @@ func migration_014_add_briefing_delivery_columns(tx *sql.Tx) error {
 
 	return nil
 }
+
+// migration_015_add_feature_notifications adds the feature_notifications table
+// for one-time feature discovery notifications.
+func migration_015_add_feature_notifications(tx *sql.Tx) error {
+	schema := `
+	CREATE TABLE IF NOT EXISTS feature_notifications (
+		event_id TEXT PRIMARY KEY,
+		fired_at INTEGER NOT NULL,
+		acknowledged_at INTEGER
+	);
+	`
+	_, err := tx.Exec(schema)
+	return err
+}

mothership/internal/help/notifier.go

@@ -53,30 +53,14 @@ const (
 )
 
 // NewNotifier creates a new feature notification manager.
+// The feature_notifications table must already exist via migration.
 func NewNotifier(db *sql.DB) (*Notifier, error) {
-	// Ensure the feature_notifications table exists
-	if err := ensureSchema(db); err != nil {
-		return nil, err
-	}
-
 	return &Notifier{
 		db:         db,
 		quietHours: &QuietHours{},
 	}, nil
 }
 
-// ensureSchema creates the feature_notifications table if it doesn't exist.
-func ensureSchema(db *sql.DB) error {
-	query := `
-	CREATE TABLE IF NOT EXISTS feature_notifications (
-		event_id TEXT PRIMARY KEY,
-		fired_at INTEGER NOT NULL,
-		acknowledged_at INTEGER
-	);`
-	_, err := db.Exec(query)
-	return err
-}
-
 // SetQuietHours sets the quiet hours configuration.
 func (n *Notifier) SetQuietHours(qh *QuietHours) {
 	n.mu.Lock()

mothership/internal/help/notifier_test.go

@@ -194,15 +194,22 @@ func TestNotifierFireWithAction(t *testing.T) {
 	}
 }
 
-// createTestDB creates an in-memory test database.
+// createTestDB creates an in-memory test database with the feature_notifications schema.
 func createTestDB(t *testing.T) *sql.DB {
 	db, err := sql.Open("sqlite", ":memory:")
 	if err != nil {
 		t.Fatalf("Failed to open test database: %v", err)
 	}
 
-	// Create schema
-	if err := ensureSchema(db); err != nil {
+	// Create the feature_notifications table directly (same as migration_015)
+	schema := `
+	CREATE TABLE IF NOT EXISTS feature_notifications (
+		event_id TEXT PRIMARY KEY,
+		fired_at INTEGER NOT NULL,
+		acknowledged_at INTEGER
+	);
+	`
+	if _, err := db.Exec(schema); err != nil {
 		t.Fatalf("Failed to create schema: %v", err)
 	}