fix: remove hardcoded localhost default arg from GET /api/keys, unify coverage to single coverage/ dir, fix test to pass explicit Request

- Remove `new Request('http://localhost/api/keys')` default arg from GET handler in src/app/api/keys/route.ts (line 26)
- Fix api-key-reveal-route.test.mjs to pass explicit Request instead of calling GET() with no args
- Add --output-dir coverage to all c8 scripts in package.json
- Add coverage.reportsDirectory: 'coverage' to vitest.config.ts and vitest.mcp.config.ts
- Fix CHANGELOG.md structure (# Changelog + [Unreleased] to top)
- Remove 30+ stale coverage-* directories from project root
- Coverage: Statements 78.76% | Branches 72.75% | Functions 80.93% | Lines 78.76% (all thresholds passed)

vitest.config.ts

@@ -18,6 +18,9 @@ export default defineConfig({
       "**/.git/**",
       "open-sse/services/autoCombo/__tests__/providerDiversity.test.ts",
     ],
+    coverage: {
+      reportsDirectory: "coverage",
+    },
   },
   plugins: [react()],
   resolve: {