Remove /generate-app: app shell is now milestone 01 of the plan

The initial app is no longer generated by a separate command. /plan-milestones
now always makes milestone 01 'App Shell Generation' (target platform asked in
the single question round): theme from design tokens, one screen per blueprint
entry, routes, reusable components — no feature logic — plus Playwright setup
and the e2e/app-shell.spec.ts smoke spec. It is executed like any other
milestone via /execute-milestones (which follows platform-ui-generation for it)
or /add-feature. Milestone 02 becomes the MVP core. All workflow diagrams,
skills, docs READMEs, AGENTS.md, and README updated; docs/design README also
gains the screen-inventory.md entry.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.opencode/skills/e2e-testing/SKILL.md

@@ -91,7 +91,7 @@ test.describe('Edit user profile', () => {
 
 ## Writing the App-Shell Smoke Spec
 
-Created by `/generate-app` (web target). `e2e/app-shell.spec.ts` must verify:
+Created by the App Shell milestone (milestone 01, web target). `e2e/app-shell.spec.ts` must verify:
 
 - The app starts and the entry screen renders.
 - Every route in `ui-blueprint.json` is reachable and renders its screen title.
@@ -108,7 +108,7 @@ npm run test:e2e
 
 ## Verification Checklist
 
-Used by `/add-feature` Step 7, `/execute-milestones` Step 2.6, and `/generate-app` Step 5:
+Used by `/add-feature` Step 7 and `/execute-milestones` Step 2.6 (including the App Shell milestone):
 
 - [ ] Playwright is set up (`test:e2e` script exists) — set it up via this skill if missing.
 - [ ] Every implemented feature has `e2e/[feature].spec.ts` covering its acceptance criteria.