docs: clarify verification script error/warning handling

- Separate error fixing (required) from warning review (informational)
- Remove ambiguous 'warnings should be reviewed' phrasing
- Align with script instruction: do not auto-fix issues
- Make clear: errors must be fixed, warnings are for acknowledgment

PROJECT_GUIDELINES.md

@@ -301,7 +301,8 @@ git checkout -- internal/handlers/auth.go
 
 ### Before Committing
 - [ ] **Run verification script**: `bash scripts/verify-guidelines.sh`
-- [ ] **Fix any errors** before committing (warnings should be reviewed)
+- [ ] **Fix any errors** - verification must pass (0 errors) to commit
+- [ ] **Review warnings** - acknowledge warnings, fix if appropriate
 - [ ] Run tests: `go test ./... -v`
 - [ ] Run lint/typecheck if available
 - [ ] Ensure no secrets in changes