fix(score): Fix P0 Issue #3 - Skill Score now uses base=50 consistently

ISSUE:
- calculateSimplifiedScore() was using base=100 for Skill Score
- calculateFullV9Score() correctly used base=50
- Inconsistency caused incorrect Skill Score calculations in fallback mode

FIX:
- Updated calculateSimplifiedScore() to use base=50 for skillCategoryScores
- Changed lines 463-467 from base=100 to base=50
- Both functions now consistently use:
  * APP Score: base=100 (repository health)
  * Skill Score: base=50 (developer skill threshold)

RATIONALE:
- base=50 distinguishes developers: 0 issues = 50/100 (passing threshold)
- Developers with issues score <50 (clear signal of problems)
- Consistent scoring across all code paths

TESTING:
- TypeScript compilation: PASSED (no errors)
- Verified in score-calculator.ts lines 459-468

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

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

Author: alpsla

packages/agents/src/two-branch/report/score-calculator.ts

@@ -456,14 +456,15 @@ export function calculateSimplifiedScore(issues: EnrichedIssue[]): any {
     codeQuality: calculateCategoryScore(issuesByCategory.codeQuality, 100)
   };
 
-  // BUG #4 FIX: Calculate skill category scores with base=100 (for Skill Score)
-  // Changed from base=50 to base=100 for better UX (0 issues = 100/100, not 50/100)
+  // P0 ISSUE #3 FIX: Calculate skill category scores with base=50 (for Skill Score)
+  // Skill Score uses base=50 to distinguish developers: 0 issues = 50/100 (passing threshold)
+  // Developers with issues score <50 (clear signal of problems needing improvement)
   const skillCategoryScores = {
-    security: calculateCategoryScore(issuesByCategory.security, 100),
-    performance: calculateCategoryScore(issuesByCategory.performance, 100),
-    architecture: calculateCategoryScore(issuesByCategory.architecture, 100),
-    dependency: calculateCategoryScore(issuesByCategory.dependency, 100),
-    codeQuality: calculateCategoryScore(issuesByCategory.codeQuality, 100)
+    security: calculateCategoryScore(issuesByCategory.security, 50),
+    performance: calculateCategoryScore(issuesByCategory.performance, 50),
+    architecture: calculateCategoryScore(issuesByCategory.architecture, 50),
+    dependency: calculateCategoryScore(issuesByCategory.dependency, 50),
+    codeQuality: calculateCategoryScore(issuesByCategory.codeQuality, 50)
   };
 
   // APP Score = MIN of all categories (weakest link)