Add built-in hard reject for projects with zero uploaded files

Projects with no files are now automatically rejected before AI
screening runs, regardless of whether a DOCUMENT_CHECK rule is
configured. This prevents the AI from incorrectly passing projects
that have no supporting documents.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/server/services/ai-filtering.ts

@@ -796,6 +796,19 @@ export async function executeFilteringRules(
     let hasFailed = false
     let hasFlagged = false
 
+    // Built-in hard check: projects with zero files always fail
+    const fileCount = project.files?.length ?? 0
+    if (fileCount === 0) {
+      ruleResults.push({
+        ruleId: '__builtin_zero_files',
+        ruleName: 'Required Documents Check',
+        ruleType: 'DOCUMENT_CHECK',
+        passed: false,
+        action: 'REJECT',
+      })
+      hasFailed = true
+    }
+
     for (const rule of nonAiRules) {
       let result: { passed: boolean; action: 'PASS' | 'REJECT' | 'FLAG' }
       if (rule.ruleType === 'FIELD_BASED') {