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>

AGENTS.md

@@ -85,7 +85,7 @@ Define "what to build" and "how to build it" for the entire application:
 - **ui-blueprint.json** - UI structure (source of truth for UI generation)
 - **platform-mapping.md** - How the design maps to Web / Flutter / WinUI 3
 - **screens/\*.svg** - Visual wireframes (references only)
-- Created by `/define-design`, updated by `/update-design`, consumed by `/generate-app` and `/add-feature`
+- Created by `/define-design`, updated by `/update-design`, consumed by the App Shell milestone (milestone 01) and `/add-feature`
 
 #### Milestone Documents (`docs/milestones/`)
 - **roadmap.md** - Overview: phase/milestone table, ordering rationale, current phase and milestone, icebox
@@ -103,7 +103,7 @@ Define "what to do this time" for a specific development task:
 ### opencode Configuration (`.opencode/`)
 
 - `.opencode/agent/` - Subagent definitions (doc-reviewer, implementation-validator)
-- `.opencode/command/` - Slash commands (setup-project, define-design, generate-app, update-design, plan-milestones, execute-milestones, add-feature, review-docs)
+- `.opencode/command/` - Slash commands (setup-project, define-design, update-design, plan-milestones, execute-milestones, add-feature, review-docs)
 - `.opencode/skills/` - Task-specific skills (prd-writing, functional-design, architecture-design, repository-structure, development-guidelines, glossary-creation, ui-design, design-tokens, platform-ui-generation, milestone-planning, milestone-execution, e2e-testing, steering)
 
 ## Development Process
@@ -114,10 +114,9 @@ Define "what to do this time" for a specific development task:
 2. Create persistent documents with `/setup-project` (automatically creating six)
 3. Define the UI/UX design with `/define-design` (creates `docs/design/`)
 4. Review and refine the UI/UX with `/update-design` (or re-run `/define-design`) until approved — before generating code
-5. Generate the initial app with `/generate-app web | flutter | winui3`
-6. Plan milestones with `/plan-milestones` (creates `docs/milestones/` with one `phase[N]-milestones.md` per phase)
-7. Implement, either way:
-   - `/execute-milestones phase1-milestones.md` — execute one phase file: its milestones one by one autonomously (one steering directory per milestone); repeat with the next phase file, or
+5. Plan milestones with `/plan-milestones` (creates `docs/milestones/` with one `phase[N]-milestones.md` per phase; milestone 01 is always App Shell Generation from the design spec)
+6. Implement, either way:
+   - `/execute-milestones phase1-milestones.md` — execute one phase file: its milestones one by one autonomously (one steering directory per milestone; milestone 01 generates the initial app); repeat with the next phase file, or
    - `/add-feature [feature]` — one feature at a time, milestone by milestone
 
 ### Day-to-Day Usage
@@ -135,7 +134,6 @@ Define "what to do this time" for a specific development task:
 
 # Design phase
 > /define-design
-> /generate-app web
 > /update-design add a profile screen
 
 # Milestone planning and execution