[codex] Polish first-run UI surfaces

[Junnyyy]

TL;DR

Polished Latch’s visible first-run demo surfaces across the Playground, module federation host/remotes, and DevTools while preserving SDK behavior, public package APIs, singleton semantics, CI setup, and the source-only/no-publishing posture.

What changed?

• Reworked DevTools override controls into explicit On/Off segmented actions with clearer accessible labels and override count visibility
• Removed the duplicate module federation host skip link while preserving the static skip link
• Refined the Playground first-run layout by moving DevTools into the primary workspace, clarifying the fail-sync action, and improving responsive panel behavior
• Tightened module federation host and remote layouts with safer mobile containment, safe-area padding, and internally scrolling flag tables
• Added focused regression coverage and recorded UI polish learnings in AGENTS.md

How to test?

1. Run pnpm --filter @latchflags/devtools test
2. Run pnpm --filter @latchflags/mf-host test
3. Run pnpm --filter @latchflags/cli build if local CLI declarations are not already present
4. Run pnpm typecheck
5. Run pnpm lint
6. Run pnpm test
7. Run pnpm build
8. Browser-check Playground and module federation preview at desktop and mobile widths, including fail sync, refetch, DevTools overrides, remote hydration, and remote toggles

Why make this change?

The first-run UI should make Latch’s SDK behavior, override model, and module federation singleton story easier to evaluate without adding product scope or changing runtime contracts. These changes improve visual hierarchy, responsive behavior, accessibility affordances, and demo clarity while keeping the implementation scoped to demo/docs/devtools surfaces.

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Note

Low Risk
Scoped to demo apps, DevTools presentation, and CSS; core flag client APIs and override semantics are unchanged aside from clearer explicit On/Off override actions in DevTools.

Overview
Polishes first-run demo surfaces (Playground, module federation host/remotes, and Latch DevTools) without changing SDK contracts.

Latch DevTools replaces boolean override checkboxes with explicit On/Off segmented controls (clearer labels, override count in the header), refreshes styling, and uses a full border shorthand on active segment buttons to avoid React dev warnings on rerender. Tests cover the new actions and the border-style regression.

Module federation host drops the in-app duplicate “Skip to content” link so only index.html owns it; a test locks that in. Layout CSS adds min-width: 0 on flag-table/DevTools grid cells, safe-area bottom padding, and tighter mobile behavior so wide tables scroll inside the panel instead of causing page-level horizontal overflow.

Playground moves DevTools into the main workspace grid, styles Fail next sync as a danger button, and adjusts responsive grid/panel headings and payload pre height. AGENTS.md records the DevTools border and min-width: 0 patterns for future demo work.

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