🤖 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/openai-responses.reasoning-replay.test.ts

@@ -115,6 +115,15 @@ describe("openai-responses reasoning replay", () => {
     expect(types).toContain("reasoning");
     expect(types).toContain("function_call");
     expect(types.indexOf("reasoning")).toBeLessThan(types.indexOf("function_call"));
+
+    const functionCall = input.find(
+      (item) =>
+        item &&
+        typeof item === "object" &&
+        (item as Record<string, unknown>).type === "function_call",
+    ) as Record<string, unknown> | undefined;
+    expect(functionCall?.call_id).toBe("call_123");
+    expect(functionCall?.id).toBe("fc_123");
   });
 
   it("still replays reasoning when paired with an assistant message", async () => {