Refactor observation handling: centralize constants and improve context settings

- Introduced `observation-metadata.ts` to define valid observation types and concepts, along with their corresponding emoji mappings.
- Updated `context-hook.ts` to utilize new constants for observation types and concepts, enhancing maintainability.
- Refactored `worker-service.ts` to validate observation types and concepts against the new centralized constants.
- Consolidated settings management in `Sidebar.tsx` to streamline state handling for context settings.
- Improved error handling and logging for context loading failures.

src/constants/observation-metadata.ts

@@ -0,0 +1,68 @@
+/**
+ * Observation metadata constants
+ * Shared across hooks, worker service, and UI components
+ */
+
+/**
+ * Valid observation types
+ */
+export const OBSERVATION_TYPES = [
+  'bugfix',
+  'feature',
+  'refactor',
+  'discovery',
+  'decision',
+  'change'
+] as const;
+
+export type ObservationType = typeof OBSERVATION_TYPES[number];
+
+/**
+ * Valid observation concepts
+ */
+export const OBSERVATION_CONCEPTS = [
+  'how-it-works',
+  'why-it-exists',
+  'what-changed',
+  'problem-solution',
+  'gotcha',
+  'pattern',
+  'trade-off'
+] as const;
+
+export type ObservationConcept = typeof OBSERVATION_CONCEPTS[number];
+
+/**
+ * Map observation types to emoji icons
+ */
+export const TYPE_ICON_MAP: Record<ObservationType | 'session-request', string> = {
+  'bugfix': '🔴',
+  'feature': '🟣',
+  'refactor': '🔄',
+  'change': '✅',
+  'discovery': '🔵',
+  'decision': '⚖️',
+  'session-request': '🎯'
+};
+
+/**
+ * Map observation types to work emoji (for token display)
+ */
+export const TYPE_WORK_EMOJI_MAP: Record<ObservationType, string> = {
+  'discovery': '🔍',  // research/exploration
+  'change': '🛠️',    // building/modifying
+  'feature': '🛠️',   // building/modifying
+  'bugfix': '🛠️',    // building/modifying
+  'refactor': '🛠️',  // building/modifying
+  'decision': '⚖️'   // decision-making
+};
+
+/**
+ * Default observation types (comma-separated string for settings)
+ */
+export const DEFAULT_OBSERVATION_TYPES_STRING = OBSERVATION_TYPES.join(',');
+
+/**
+ * Default observation concepts (comma-separated string for settings)
+ */
+export const DEFAULT_OBSERVATION_CONCEPTS_STRING = OBSERVATION_CONCEPTS.join(',');