[codex] Redesign launcher and overlay UI from Stitch specs

[Emperiusm]

What changed

This PR ports the approved Stitch redesign into PRISM's native Rust immediate-mode UI across the launcher and in-session overlay.

Highlights:

• redesigned Home with a hero quick-connect flow and recent-connections row mode
• refreshed Saved Connections card styling and add-connection affordance
• redesigned Profiles with a new native segmented control widget
• reworked Settings into a single scrollable page while preserving immediate-save behavior
• restyled the overlay capsule and bottom session bar while preserving the existing dropdown-panel interaction model
• extended shared theme tokens to support the new visual language

Why it changed

The existing launcher and overlay no longer matched the approved Stitch direction. This update brings the native PRISM UI in line with the redesign without introducing web views, routing changes, or new non-native state models.

User impact

• clearer hierarchy and stronger visual polish across all launcher screens
• faster Home reconnect flow
• more legible Profiles and Settings editing surfaces
• more cohesive overlay controls with restored runtime profile switching and a clear disconnect affordance

Validation

• cargo test -p prism-client

Notes

• Overlay keeps PRISM's capsule + dropdown panel model instead of adopting a persistent sidebar
• Settings remains a single scrollable page instead of adding sub-navigation

[github-actions]

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[Emperiusm]

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