🤖 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/transcript-policy.ts

@@ -95,7 +95,7 @@ export function resolveTranscriptPolicy(params: {
 
   const needsNonImageSanitize = isGoogle || isAnthropic || isMistral || isOpenRouterGemini;
 
-  const sanitizeToolCallIds = isGoogle || isMistral || isAnthropic || isOpenAi;
+  const sanitizeToolCallIds = isGoogle || isMistral || isAnthropic;
   const toolCallIdMode: ToolCallIdMode | undefined = isMistral
     ? "strict9"
     : sanitizeToolCallIds
@@ -109,7 +109,7 @@ export function resolveTranscriptPolicy(params: {
 
   return {
     sanitizeMode: isOpenAi ? "images-only" : needsNonImageSanitize ? "full" : "images-only",
-    sanitizeToolCallIds,
+    sanitizeToolCallIds: !isOpenAi && sanitizeToolCallIds,
     toolCallIdMode,
     repairToolUseResultPairing: !isOpenAi && repairToolUseResultPairing,
     preserveSignatures: isAntigravityClaudeModel,