feat(github): add complexity labels with heuristic detection

- Add complexity dropdown to feature request template
- Auto-detect complexity from dropdown selection
- Heuristic fallback based on: checklist count, code blocks,
  section headers, file references, and keywords

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

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -43,3 +43,16 @@ body:
     attributes:
       label: Alternatives considered
       description: Any other approaches you've thought about?
+
+  - type: dropdown
+    id: complexity
+    attributes:
+      label: Estimated complexity
+      description: How much work do you think this requires?
+      options:
+        - "Small - Quick fix, single file, < 1 hour"
+        - "Medium - Multiple files, few hours to a day"
+        - "Large - Significant changes, multiple days"
+        - "Unknown - Not sure"
+    validations:
+      required: false

.github/workflows/auto-label.yml

@@ -52,9 +52,39 @@ jobs:
               labelsToAdd.push('agentic');
             }
 
-            // Complexity hints
-            if (content.includes('simple') || content.includes('quick fix') || content.includes('typo')) {
+            // Complexity - from template dropdown or heuristics
+            if (body.includes('small - quick fix')) {
+              labelsToAdd.push('complexity:small');
               labelsToAdd.push('good first issue');
+            } else if (body.includes('medium - multiple files')) {
+              labelsToAdd.push('complexity:medium');
+            } else if (body.includes('large - significant')) {
+              labelsToAdd.push('complexity:large');
+            } else if (!body.includes('unknown - not sure')) {
+              // Heuristic complexity detection
+              const checklistCount = (body.match(/- \[ \]/g) || []).length;
+              const codeBlocks = (body.match(/```/g) || []).length / 2;
+              const sections = (body.match(/^##/gm) || []).length;
+              const fileRefs = (body.match(/\.(go|php|js|ts|yml|yaml|json|md)\b/g) || []).length;
+
+              const complexKeywords = ['refactor', 'rewrite', 'migration', 'breaking change', 'across repos', 'architecture'];
+              const simpleKeywords = ['simple', 'quick fix', 'typo', 'minor', 'trivial'];
+
+              const hasComplexKeyword = complexKeywords.some(k => content.includes(k));
+              const hasSimpleKeyword = simpleKeywords.some(k => content.includes(k));
+
+              let score = checklistCount * 2 + codeBlocks + sections + fileRefs;
+              score += hasComplexKeyword ? 5 : 0;
+              score -= hasSimpleKeyword ? 3 : 0;
+
+              if (hasSimpleKeyword || score <= 2) {
+                labelsToAdd.push('complexity:small');
+                labelsToAdd.push('good first issue');
+              } else if (score <= 6) {
+                labelsToAdd.push('complexity:medium');
+              } else {
+                labelsToAdd.push('complexity:large');
+              }
             }
 
             // Apply labels if any detected