fix(session-sync): add type guard for estimated_cost_usd to prevent NOT NULL errors (#314)

Fixes remaining NOT NULL constraint failures after PR #312.

Problem:
- Even with COALESCE in SQL, some sessions still fail with NOT NULL error
- Hermes may return undefined/null/NaN values that pass through COALESCE

Solution:
- Add explicit type guard: `typeof value === 'number'`
- Only use the value if it's a valid number, otherwise default to 0
- This ensures we never pass undefined/null/NaN to the database

Related to issue #308

packages/server/src/services/hermes/session-sync.ts

@@ -215,6 +215,10 @@ function syncProfileSessions(profile: string): {
           }
 
           // Update session with Hermes data
+          const estimatedCost = typeof hermesSession.estimated_cost_usd === 'number'
+            ? hermesSession.estimated_cost_usd
+            : 0
+
           updateSession(newSessionId, {
             started_at: hermesSession.started_at,
             ended_at: hermesSession.ended_at,
@@ -224,7 +228,7 @@ function syncProfileSessions(profile: string): {
             cache_read_tokens: hermesSession.cache_read_tokens,
             cache_write_tokens: hermesSession.cache_write_tokens,
             reasoning_tokens: hermesSession.reasoning_tokens,
-            estimated_cost_usd: hermesSession.estimated_cost_usd || 0,
+            estimated_cost_usd: estimatedCost,
             last_active: hermesSession.started_at, // Use started_at as fallback since last_active doesn't exist in Hermes state.db
             preview,
           })