feat(integrations): add Google Health (Fit) integration with full permissions

OAuth2 flow with all 11 Google Fitness scopes (activity, body, sleep,
heart rate, nutrition, location, blood glucose/pressure/temperature,
oxygen saturation, reproductive health). Stores access + refresh tokens;
auto-refreshes on expiry.

GoogleHealthSignalSource fetches steps, sleep sessions, active minutes,
calories, and heart rate from the Fit aggregate + sessions APIs. Signals
flow into both the tip orchestrator and the health-vitals pre-compute
agent, which generates prompt snippets about step progress, sleep
deficit, sedentary time, and elevated heart rate.

Signal.kind extended with 'health'; IntegrationProvider extended with
'google-health'. Agent compute signal mapping enriched to include source,
kind, and all features so health-vitals can filter its own signals.

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

packages/shared-types/src/http/integrations.ts

@@ -1,4 +1,4 @@
-export type IntegrationProvider = 'todoist';
+export type IntegrationProvider = 'todoist' | 'google-health';
 export type IntegrationStatus = 'connected' | 'disconnected' | 'error';
 
 export interface Integration {

packages/shared-types/src/http/signal.ts

@@ -2,7 +2,7 @@
 export interface Signal {
   id: string;
   source: string;                             // e.g. 'todoist', 'google-calendar', 'manual'
-  kind: 'task' | 'event' | 'habit' | 'insight';
+  kind: 'task' | 'event' | 'habit' | 'insight' | 'health';
   content: string;
   metadata: Record<string, unknown>;          // source-specific raw fields
   features: Record<string, number | boolean>; // bandit-ready numeric/boolean features