Merge remote-tracking branch 'origin/codex/invariant-service-seam' into codex/invariant-package-registration-gate

# Conflicts:
#	.agents/notes/implemented/architecture/2026-07-19-package-owned-invariant-service.i18n.yaml
#	docs/core-data-structures/session.md
#	docs/module-graph.md
#	package.json
#	packages/sdk/scripts/tsconfig.json

packages/llm/llm-deepseek/src/adapter.ts

@@ -91,6 +91,9 @@ export class DeepSeekAdapter extends LlmAdapter {
         'content-type': 'application/json',
         'accept': 'text/event-stream',
         ...attributionHeaders(),
+        ...options.sessionId !== undefined
+          ? { 'x-deepseek-harness-session-id': String(options.sessionId) }
+          : {},
       },
       body: JSON.stringify(body),
       ...options.signal ? { signal: options.signal } : {},