feat: isolate Claude and Codex session sources

Persist platform_source across session creation, transcript ingestion, API query paths, and viewer state so Claude and Codex data can coexist without bleeding into each other.

- add platform-source normalization helpers and persist platform_source in sdk_sessions via migration 24 with backfill and indexing
- thread platformSource through CLI hooks, transcript processing, context generation, pagination, search routes, SSE payloads, and session management
- expose source-aware project catalogs, viewer tabs, context preview selectors, and source badges for observations, prompts, and summaries
- start the transcript watcher from the worker for transcript-based clients and preserve platform source during Codex ingestion
- auto-start the worker from the MCP server for MCP-only clients and tighten stdio-driven cleanup during shutdown
- keep createSDKSession backward compatible with existing custom-title callers while allowing explicit platform source forwarding

src/ui/viewer/components/SummaryCard.tsx

@@ -21,6 +21,9 @@ export function SummaryCard({ summary }: SummaryCardProps) {
       <header className="summary-card-header">
         <div className="summary-badge-row">
           <span className="card-type summary-badge">Session Summary</span>
+          <span className={`card-source source-${summary.platform_source || 'claude'}`}>
+            {summary.platform_source || 'claude'}
+          </span>
           <span className="summary-project-badge">{summary.project}</span>
         </div>
         {summary.request && (