feat(usage): add Hermes Agent tracking + fix zero-cost bug + perf

Hermes:
- Parse ~/.hermes/state.db sessions (incl. profiles/*/state.db) into
  proxy_request_logs with data_source='hermes_session', WAL-aware
  incremental sync, Hermes-reported cost preferred over model_pricing
  fallback

Zero-cost bug (dashboard showed \$0 totals):
- GPT-5.5 family default pricing (~83% of affected rows used GPT-5.5)
- find_model_pricing_row: ASCII-lowercase normalization so
  "OpenAI/GPT-5.5@HIGH" matches seeded "gpt-5.5"
- Startup cost backfill in async task: scan rows where total_cost <= 0
  but tokens > 0, recompute via model_pricing in a single transaction

Performance:
- Add (app_type, created_at DESC) covering index for dashboard range
  queries
- Add expression index on COALESCE(data_source, 'proxy') so dedup EXISTS
  subqueries use index lookup instead of full scan; drop superseded
  idx_request_logs_dedup_lookup

Refactor:
- row_to_request_log_detail helper (3-way de-dup; fixes cost_multiplier
  \"1\" vs \"1.0\" drift between callers)
- Promote get_sync_state/update_sync_state to shared session_usage
  module (4 copies -> 1)
- run_step helper in lib.rs replaces 9 if-let-Err blocks
- maybe_backfill_log_costs returns bool to skip duplicate total_cost
  parsing in caller

src/components/usage/DataSourceBar.tsx

@@ -17,6 +17,7 @@ const DATA_SOURCE_ICONS: Record<string, React.ReactNode> = {
   codex_db: <Database className="h-3.5 w-3.5" />,
   codex_session: <FileText className="h-3.5 w-3.5" />,
   gemini_session: <FileText className="h-3.5 w-3.5" />,
+  hermes_session: <Database className="h-3.5 w-3.5" />,
 };
 
 export function DataSourceBar({ refreshIntervalMs }: DataSourceBarProps) {

src/components/usage/RequestLogTable.tsx

@@ -141,6 +141,7 @@ export function RequestLogTable({
               <SelectItem value="claude">Claude</SelectItem>
               <SelectItem value="codex">Codex</SelectItem>
               <SelectItem value="gemini">Gemini</SelectItem>
+              <SelectItem value="hermes">Hermes</SelectItem>
             </SelectContent>
           </Select>
 

src/components/usage/UsageDashboard.tsx

@@ -35,6 +35,7 @@ const APP_FILTER_OPTIONS: AppTypeFilter[] = [
   "claude",
   "codex",
   "gemini",
+  "hermes",
 ];
 
 export function UsageDashboard() {