v0.6.5: Renderer pipeline, docs rewrite, architecture diagrams

Lift block rendering to kernel SDK primitives (sw.renderers + sw.markdown)
so all surfaces share one markdown pipeline. Rewrite docs for external
audience — remove all fork history references. Add Mermaid architecture
diagrams, CONTRIBUTING guide, and extension tutorial.

- sw.renderers SDK module: kernel-level renderer registry
- sw.markdown SDK module: unified marked v16 + DOMPurify pipeline
- Browser extension script loader for renderer injection
- Notes + Docs surfaces migrated to sw.markdown.renderSync()
- 4 renderer extensions rewritten to IIFE + sw.renderers.register()
- 6 Mermaid diagrams in ARCHITECTURE.md
- CONTRIBUTING.md + TUTORIAL-FIRST-EXTENSION.md
- DESIGN-WORKFLOWS.md replaces fork-era design doc
- Surface alias routes removed from main.go
- ICD/SDK runners migrated to /admin/packages/ endpoints
- 13 new renderer tests
- Docs, CHANGELOG, ROADMAP cleaned of fork references

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/icd-test-runner/js/crud/editor-package.js

@@ -68,9 +68,9 @@
       T.assert(d.version === '0.31.0', 'version mismatch');
     });
 
-    await T.test('crud', 'editorPackage', 'edpkg: GET /admin/surfaces (editor in list)', async function () {
-      var d = await T.apiGet('/admin/surfaces');
-      T.assertHasKey(d, 'data', '/admin/surfaces');
+    await T.test('crud', 'editorPackage', 'edpkg: GET /admin/packages (editor in list)', async function () {
+      var d = await T.apiGet('/admin/packages');
+      T.assertHasKey(d, 'data', '/admin/packages');
       var found = d.data.some(function (s) { return s.id === 'editor'; });
       T.assert(found, 'editor package should appear in surfaces list');
     });
@@ -78,7 +78,7 @@
     await T.test('crud', 'editorPackage', 'edpkg: core /editor removed (404)', async function () {
       // The old /editor route should no longer exist — it was removed in CS1.
       // We test by checking the surfaces list for a core editor entry.
-      var d = await T.apiGet('/admin/surfaces');
+      var d = await T.apiGet('/admin/packages');
       var surfaces = d.data || [];
       var coreEditor = surfaces.find(function (s) { return s.id === 'editor' && s.source === 'core'; });
       T.assert(!coreEditor, 'no core editor surface should exist — editor is now a package');
@@ -139,7 +139,7 @@
 
     await T.test('crud', 'editorPackage', 'edpkg: editor in extension nav items', async function () {
       // When installed, editor should appear in the surfaces list as an extension surface
-      var d = await T.apiGet('/admin/surfaces');
+      var d = await T.apiGet('/admin/packages');
       var surfaces = d.data || [];
       var editorSurface = surfaces.find(function (s) { return s.id === 'editor'; });
       T.assert(editorSurface, 'editor should be in surfaces list');