fix(codex): retry server overloaded turns

[gpYang]

Summary

• classify Codex server_overloaded/capacity failures as retriable
• retry overloaded/rate-limit turns instead of surfacing raw failures
• render retry notices in rich/progress cards instead of standalone messages
• bypass progress-card edit throttling for retry notices and finalize old retry cards before replay/exhaustion

Validation

• go build -o /tmp/cc-connect-retry.candidate ./cmd/cc-connect
• go test ./core -run 'TestProcessInteractiveTurnWithRetry_(ReplaysPromptAfterOverloaded|RichCardNoticeUpdatesCard|ProgressCardNoticeUpdatesCard|ProgressCardRetryExhaustionFinalizesFailed|ProgressCardRetryNoticeBypassesThrottle|StopCancelsRetryDelay|ReplaysQueuedPromptAfterOverloaded)|TestProcessInteractiveEvents_ReturnsRetriableErrorWithoutSendingRawError|TestCompactProgressWriter|TestBuildAndParseProgressCardPayload|TestParseProgressCardPayload' -count=3
• go test ./core -run 'TestProcessInteractiveTurnWithRetry_(ProgressCardRetryExhaustionFinalizesFailed|ProgressCardRetryNoticeBypassesThrottle|RichCardNoticeUpdatesCard|ProgressCardNoticeUpdatesCard|StopCancelsRetryDelay)' -count=1 -race
• go test ./agent/codex -run 'TestSend_TurnFailedServerOverloadedIsRetriable|TestSend_WithImages_PassesImageArgsAndDefaultPrompt|TestSend_ResumeWithImages_PlacesSessionBeforeImageFlags|TestSend_HandlesLargeJSONLines|TestGetModelAndReasoningEffort_FromRuntimeConfigWhenUnset' -count=3 -p 1 -parallel=1
• go test ./platform/feishu ./platform/discord ./platform/telegram -count=1
• go test ./core -run TestCUJ_A3_ImageReachesAgent -count=3

Note: built candidate only; did not replace or restart the local cc-connect service.