Document intentional error suppressions with comments (gt-zn9m)

All 156 instances of _ = error suppression in non-test code now have
explanatory comments documenting why the error is intentionally ignored.

Categories of intentional suppressions:
- non-fatal: session works without these - tmux environment setup
- non-fatal: theming failure does not affect operation - visual styling
- best-effort cleanup - defer cleanup on failure paths
- best-effort notification - mail/notifications that should not block
- best-effort interrupt - graceful shutdown attempts
- crypto/rand.Read only fails on broken system - random ID generation
- output errors non-actionable - fmt.Fprint to io.Writer

This addresses the silent failure and debugging concerns raised in the
issue by making the intentionality explicit in the code.

Generated with Claude Code https://claude.com/claude-code

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/git/git.go

@@ -277,24 +277,24 @@ func (g *Git) CheckConflicts(source, target string) ([]string, error) {
 		// Check if there are unmerged files (indicates conflict)
 		conflicts, err := g.getConflictingFiles()
 		if err == nil && len(conflicts) > 0 {
-			// Abort the test merge
+			// Abort the test merge (best-effort cleanup)
 			_ = g.AbortMerge()
 			return conflicts, nil
 		}
 
 		// Check if it's a conflict error from wrapper
 		if errors.Is(mergeErr, ErrMergeConflict) {
-			_ = g.AbortMerge()
+			_ = g.AbortMerge() // best-effort cleanup
 			return conflicts, nil
 		}
 
-		// Some other merge error
+		// Some other merge error (best-effort cleanup)
 		_ = g.AbortMerge()
 		return nil, mergeErr
 	}
 
 	// Merge succeeded (no conflicts) - abort the test merge
-	// Use reset since --abort won't work on successful merge
+	// Use reset since --abort won't work on successful merge (best-effort cleanup)
 	_, _ = g.run("reset", "--hard", "HEAD")
 	return nil, nil
 }