Handle transient Sentry envelope SSL upload failures

[cursor]

Summary

• add bounded retry handling for transient Sentry envelope upload failures (SSLError, ConnectionError, Timeout) in GithubClient._send_envelope
• set a request timeout for envelope uploads to avoid hanging requests
• after retry exhaustion, log a warning and return without raising to avoid turning transient ingest/network issues into webhook 500s
• add focused unit tests covering retry success and retry exhaustion behavior

Root Cause

Sentry issue SENTRY-GITHUB-ACTIONS-APP-4E shows intermittent TLS/connection failures while posting envelopes to Sentry ingest from src/github_sdk.py (requests.post in _send_envelope). These are transient transport failures outside payload generation logic but were previously unhandled, bubbling up to src/main.py and generating noisy application errors.

Validation

• python3 -m pytest tests/test_github_sdk.py
• Result: 9 passed

Risk / Notes

• This intentionally suppresses only transient network/TLS upload exceptions for telemetry forwarding; non-transient HTTP failures (raise_for_status) are still surfaced.
• A bounded retry count and timeout keep behavior predictable while reducing production error noise.