feat: v0.5.16 - migrate to Responses API (#586)

* refactor: migrate from /v1/runs to /v1/responses streaming API

Replace EventSource-based polling with direct SSE streaming via the
/v1/responses endpoint across all server-side callers (chat-run-socket,
context-compressor, gateway-client, agent-clients). Messages are now
written to DB in real-time during streaming, eliminating post-run sync.
Frontend chat store adds tool_call_id tracking for deduplication.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* chore: bump version to 0.5.16 and add changelog

- Persist real API usage to usage table on response.completed
- Remove unused codex_reasoning_items field from message schema
- Fix unused variable warnings in chat-run-socket
- Bump version to 0.5.16
- Add changelog entries for 0.5.16 (8 locales)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

packages/client/src/data/changelog.ts

@@ -5,6 +5,16 @@ export interface ChangelogEntry {
 }
 
 export const changelog: ChangelogEntry[] = [
+  {
+    version: '0.5.16',
+    date: '2026-05-10',
+    changes: [
+      'changelog.new_0_5_16_1',
+      'changelog.new_0_5_16_2',
+      'changelog.new_0_5_16_3',
+      'changelog.new_0_5_16_4',
+    ],
+  },
   {
     version: '0.5.15',
     date: '2026-05-09',