Simplify Skill Structure to show only the skills directory

The config files, assets, scripts, schemas, and references are already
described in the Shared Support Layer section. The structure tree now
focuses on what skill users care about: the six skills and their
reference files.

README.md

@@ -217,55 +217,31 @@ The skills share:
 ## Skill Structure
 <!-- BEGIN SKILL STRUCTURE -->
 ```text
-xcode-build-optimization-agent-skill/
-  .claude-plugin/
-    marketplace.json
-    plugin.json
-  .cursor-plugin/
-    plugin.json
-  agents/
-    openai.yaml
-  assets/
-    logo.svg
-    xcode-build-optimization-banner.jpg
-  references/
-    benchmark-artifacts.md
-    build-optimization-sources.md
-    build-settings-best-practices.md
-    recommendation-format.md
-  schemas/
-    build-benchmark.schema.json
-  scripts/
-    benchmark_builds.py
-    diagnose_compilation.py
-    generate_optimization_report.py
-    render_recommendations.py
-    summarize_build_timing.py
-  skills/
-    xcode-build-benchmark/
-      SKILL.md
-      references/
-        benchmarking-workflow.md - Benchmark contract, clean vs incremental rules, and artifact expectations
-    xcode-compilation-analyzer/
-      SKILL.md
-      references/
-        code-compilation-checks.md - Swift compile hotspot checks and code-level heuristics
-    xcode-project-analyzer/
-      SKILL.md
-      references/
-        project-audit-checks.md - Build setting, script phase, and dependency audit checklist
-    spm-build-analysis/
-      SKILL.md
-      references/
-        spm-analysis-checks.md - Package graph, plugin overhead, and module variant review guide
-    xcode-build-orchestrator/
-      SKILL.md
-      references/
-        orchestration-report-template.md - Prioritization, approval, and verification report template
-    xcode-build-fixer/
-      SKILL.md
-      references/
-        fix-patterns.md - Concrete before/after patterns for each fix category
+skills/
+  xcode-build-benchmark/
+    SKILL.md
+    references/
+      benchmarking-workflow.md
+  xcode-compilation-analyzer/
+    SKILL.md
+    references/
+      code-compilation-checks.md
+  xcode-project-analyzer/
+    SKILL.md
+    references/
+      project-audit-checks.md
+  spm-build-analysis/
+    SKILL.md
+    references/
+      spm-analysis-checks.md
+  xcode-build-orchestrator/
+    SKILL.md
+    references/
+      orchestration-report-template.md
+  xcode-build-fixer/
+    SKILL.md
+    references/
+      fix-patterns.md
 ```
 <!-- END SKILL STRUCTURE -->