fix: clarify PR env override examples

[vigneshrajsb]

Summary

Improves the PR status comment guidance for environment overrides so the examples are clearer and safer to copy.

What Changed

• replaced the single inline example with a short commented instruction block
• added two dummy examples: a boolean flag and a lifecycle-themed URL
• made the parser trim each line instead of removing all spaces, so values with spaces are preserved
• added focused tests proving commented examples are ignored and real ENV: lines still parse correctly

Why

Users were getting confused by the existing example format, and the parser behavior around spaces was stricter than necessary.

Validation

• pnpm test -- --runTestsByPath src/server/lib/__tests__/comment.test.ts