fix(coverage): compare overall on shared files and cover compact edges

Deleting 100%-covered packages such as recovery falsely regressed overall
percent against merge-base. Baseline overall now uses only files still
present in the candidate profile, with a 0.1pp CI tolerance. Also exercise
stripSchemaValueCompact nested map/slice branches.

Co-authored-by: Cursor <cursoragent@cursor.com>

.github/workflows/ci.yml

@@ -1175,7 +1175,7 @@ jobs:
           FULL_SUITE: ${{ needs.lint.outputs.full_suite }}
           COVERAGE_TARGET: "100"
           COVERAGE_ENFORCE_OVERALL: "false"
-          COVERAGE_OVERALL_TOLERANCE: "0"
+          COVERAGE_OVERALL_TOLERANCE: "0.1"
         run: |
           policy_profile=coverage-policy.txt
           if [ "$FULL_SUITE" != true ]; then