refactor(webserver): extract SPA dist serving to the frontend-static fallback seat

The webserver's built-in static dist serving becomes a single-owner fallback
seat (registerFallback/applyIndexTaps); the SPA server moves to the new
@deepseek-ai/dsh-frontend-static plugin so the composing application owns its
dist as composition, not carrier config. distIndex leaves the webserver
schema; unclaimed fallback answers 404.

scripts/verify-package-readme-model-experience.ts

@@ -86,6 +86,9 @@ const SENTENCE_MODEL_EXPERIENCE: Readonly<Record<string, SentenceContract>> = {
   'packages/host/directory-picker-browse': { kind: 'none', reason: 'The GUI-host picking backend registers no model surface.' },
   'packages/host/directory-picker-native': { kind: 'none', reason: 'The GUI-host picking backend registers no model surface.' },
   'packages/host/webserver': { kind: 'none', reason: 'The HTTP carrier bridges browser and API handler and registers no model surface.' },
+  'packages/host/frontend-static': { kind: 'none', reason: 'The SPA dist server answers browser asset requests and registers no model surface.' },
+  'packages/bundle/base': { kind: 'indirect', reason: 'The bundle is a patch-list carrier; each inserted row\'s package owns its model surface.' },
+  'packages/bundle/headless': { kind: 'none', reason: 'The one-shot runner submits the task as an ordinary user message; prompts and tools belong to the composed base/web bundles.' },
   'packages/llm/llm': { kind: 'none', reason: 'The adapter registry forwards already-assembled requests unchanged.' },
   'packages/llm/token-meter': { kind: 'indirect', reason: 'The measurement service leaves model-visible changes to its consumers.' },
   'packages/lsp/lsp': { kind: 'indirect', reason: 'The provider registry delegates model rendering to dsh-tool-lsp.' },