🤖 fix: preserve openai reasoning replay ids (#17792)

What:
- disable tool-call id sanitization for OpenAI/OpenAI Codex transcript policy
- gate id sanitization in image sanitizer to full mode only
- keep orphan reasoning downgrade scoped to OpenAI model-switch replay path
- update transcript policy, session-history, sanitizer, and reasoning replay tests
- document OpenAI model-switch orphan-reasoning cleanup behavior in transcript hygiene reference

Why:
- OpenAI Responses replay depends on canonical call_id|fc_id pairings for reasoning followers
- strict id rewriting in OpenAI path breaks follower matching and triggers rs_* orphan 400s
- limiting scope avoids behavior expansion while fixing the identified regression

Tests:
- pnpm vitest run src/agents/transcript-policy.test.ts src/agents/pi-embedded-runner.sanitize-session-history.test.ts src/agents/openai-responses.reasoning-replay.test.ts
- pnpm vitest run --config vitest.e2e.config.ts src/agents/transcript-policy.e2e.test.ts src/agents/pi-embedded-runner.sanitize-session-history.e2e.test.ts src/agents/pi-embedded-helpers.sanitize-session-messages-images.removes-empty-assistant-text-blocks-but-preserves.e2e.test.ts src/agents/pi-embedded-helpers.sanitizeuserfacingtext.e2e.test.ts
- pnpm lint
- pnpm format:check
- pnpm check:docs
- pnpm test (fails in current macOS bash 3.2 env at test/git-hooks-pre-commit.integration.test.ts: mapfile not found)

src/agents/pi-embedded-runner.sanitize-session-history.e2e.test.ts

@@ -52,7 +52,7 @@ describe("sanitizeSessionHistory e2e smoke", () => {
     );
   });
 
-  it("applies strict tool-call sanitization for openai-responses", async () => {
+  it("keeps images-only sanitize policy without tool-call id rewriting for openai-responses", async () => {
     vi.mocked(helpers.isGoogleModelApi).mockReturnValue(false);
 
     await sanitizeSessionHistory({
@@ -68,8 +68,7 @@ describe("sanitizeSessionHistory e2e smoke", () => {
       "session:history",
       expect.objectContaining({
         sanitizeMode: "images-only",
-        sanitizeToolCallIds: true,
-        toolCallIdMode: "strict",
+        sanitizeToolCallIds: false,
       }),
     );
   });