feat: add diagnostic web app shell

.planning/STATE.md

@@ -7,7 +7,7 @@ See: `.planning/PROJECT.md` (updated 2026-04-26)
 **Core value:** The user should feel and prove that they are becoming more
 interview-ready after each short practice loop.
 
-**Current focus:** v2 Frontend MVP milestone started; ready for Phase 7.
+**Current focus:** Phase 8 planning: Learning Progress View.
 
 ## Current Decisions
 
@@ -37,10 +37,11 @@ interview-ready after each short practice loop.
   tech-debt items recorded in `.planning/v1-MILESTONE-AUDIT.md`.
 - v2 Frontend MVP milestone selected to turn the backend learning loop into a
   usable web service.
+- Phase 7 web app shell and diagnostic start UI is implemented and verified.
 
 ## Next Actions
 
-1. Plan and execute Phase 7: Web App Shell and Diagnostic Start.
+1. Plan and execute Phase 8: Learning Progress View.
 2. Verify the production OpenAI image model identifier before real image
    generation calls.
 3. Add standardized SUMMARY frontmatter or Nyquist validation files if future
@@ -76,6 +77,9 @@ interview-ready after each short practice loop.
   real image generation, and Nyquist validation artifacts remain deferred.
 - 2026-04-26: v2 Frontend MVP milestone started with WEB-01..WEB-08 mapped to
   phases 7 through 9.
+- 2026-04-26: Phase 7 implementation verified with `go test ./...`, OpenSpec
+  validation, root/asset HTTP smoke, and diagnostic API smoke through the
+  server used by the web app.
 
 ---
 *State initialized: 2026-04-26.*