Harden long research prompt timeouts

[crankshift]

Summary

• Increase the gateway prompt completion default to 35 minutes so it stays above a 30-minute provider timeout.
• Add project OpenCode provider timeout config for 30-minute Anthropic requests.
• Add safe timeout-specific Telegram failure replies and structured error metadata for nested OpenCode prompt errors.
• Update docs, changelog, release version, and timeout tests.

Verification

• pnpm run lint
• pnpm test
• pnpm run check

Closes #57