fix: simplify debug logging for PR number detection (EME-362)

Reduced excessive debug logging in get_github_pr_number() from 4 debug
statements to 2 essential ones. This removes the intermediate "Extracted PR
reference" and "Parsing PR number from" messages while keeping the most
important logs for debugging: event type mismatch and final PR number
detection.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: runningcode

src/utils/vcs.rs

@@ -350,10 +350,7 @@ pub fn get_github_pr_number() -> Option<u32> {
     }
 
     let pr_number_str = github_ref.strip_prefix("refs/pull/")?;
-    debug!("Extracted PR reference: {}", pr_number_str);
-
     let pr_number_str = pr_number_str.split('/').next()?;
-    debug!("Parsing PR number from: {}", pr_number_str);
 
     let pr_number = pr_number_str.parse().ok()?;
     debug!("Auto-detected PR number from GitHub Actions: {}", pr_number);