fix(sisyphus-agent): remove 30min timeout and add realtime output buffering

- Remove DEFAULT_TIMEOUT_MS (set to 0) to allow CI agent runs to complete without timeout
- Add stdbuf -oL -eL for unbuffered realtime output in GitHub Actions
- Update timeout logic to only set timeout when value > 0

This fixes CI agent runs that were timing out after 30 minutes and not showing realtime output.

🤖 Generated with assistance of OhMyOpenCode

.github/workflows/sisyphus-agent.yml

@@ -338,7 +338,7 @@ jobs:
           PROMPT="${PROMPT//BRANCH_PLACEHOLDER/$DEFAULT_BRANCH}"
           PROMPT="${PROMPT//COMMENT_PLACEHOLDER/$USER_COMMENT}"
 
-          bun run dist/cli/index.js run "$PROMPT"
+          stdbuf -oL -eL bun run dist/cli/index.js run "$PROMPT"
 
       # Push changes (as sisyphus-dev-ai)
       - name: Push changes