feat: replace dashboard landing with desktop shell frame

[ksamaschke]

Summary

• replace the hero-led main window landing with an explicit desktop shell frame
• add shell-frame RED coverage and keep adjacent desktop shell UX checks green
• remove obsolete hero/dashboard layout primitives after the frame conversion

Changes

• updated the app entry wrapper and installer dashboard shell composition for a desktop-first renderer frame
• added a focused shell-frame regression test for hero removal and desktop shell markers
• cleaned up now-unused dashboard landing styles without changing later-scope settings or route ownership work

Test Plan

• npm run build:quick
• node --test dist/tests/installer/desktop-shell-frame-red-phase.test.js
• node --test dist/tests/installer/desktop-shell-ux.test.js

Breaking Changes

• None

[ksamaschke]

ICA-REVIEW
ICA-REVIEW-RECEIPT
Reviewer-Stage: 3 (temp checkout)
Reviewer-Agent: reviewer (subagent)
PR: #251
Base: dev
Head-SHA: 9dc6353
Date-UTC: 2026-03-14T19:55:03Z

Findings: 0
NO FINDINGS

Checks/Tests:

• npm run build:quick (PASS)
• node --test dist/tests/installer/desktop-shell-frame-red-phase.test.js (PASS)
• node --test dist/tests/installer/desktop-shell-ux.test.js (PASS)

Notes:

• Reviewed in a fresh temp checkout cloned from the current branch head.

Result: PASS

[ksamaschke]

ICA-SECURITY-REVIEW
ICA-SECURITY-REVIEW-RECEIPT
Security-Reviewer-Stage: post-pr (temp checkout)
Security-Reviewer-Agent: security reviewer (subagent)
Security-Reviewer-Execution: dedicated-security-subagent
Security-Reviewer-Executor: github:ksamaschke
Security-Reviewer-Run-ID: sec-20260314T195504Z-9dc63538e4d0
PR: #251
Base: dev
Head-SHA: 9dc6353
Date-UTC: 2026-03-14T19:55:03Z

Findings: 0
NO FINDINGS

Result: PASS