TV UI foundation: introduce a real ten-foot responsive layout system, not 960x540 stretching #156

Parent: #153. Coordinate with #78 device/output profiles, #111 primary navigation and existing Theme/QML shell.

Current implementation and problem

src/qml/Main.qml builds a single centered viewport at Theme.viewportWidth=960, Theme.viewportHeight=540 and applies scale: Math.min(window.width/width, window.height/height). Theme.qml and many pages use fixed logical geometry/font sizes. This makes a TV look like a scaled-up handheld chassis, not a purpose-built couch UI.

Product goal

Deliver two coordinated presentation profiles over one shared feature/service/navigation backend:

• Handheld — current compact TrainerOS/physical-device aesthetic and reliable 960×540 controller navigation.
• TV / ten-foot — a composition designed for living-room viewing on 1080p/4K televisions, with larger readable content, fewer cramped regions, clear focus and couch-friendly navigation.

Do not fork Social, library, emulators or controller semantics into 'TV TrainerOS'. Use shared data/controllers and responsive components/layout presenters.

Layout architecture

• Add explicit app-level presentationProfile/viewingContext rather than using raw screen pixel size as a synonym for viewing distance.
• Support Auto / Handheld / TV preference: auto may use external-display/device-profile signals, but user override is authoritative (large desktop monitors are not automatically televisions).
• Replace one globally scaled 960×540 geometry with profile-aware layout tokens: effective usable surface, safe area, content density, gutters, typography, media size, focus style, row/card sizing, max readable line lengths, modal/dialog layout.
• A 4K TV should show a carefully composed amount of content at comfortably readable physical size, not tiny 4× more controls or the same handheld screen blown up 4×.
• Avoid hard-coded pixel coordinates in feature UI where composition genuinely differs; keep existing Theme colors, branding and visual identity.
• TV is landscape-first. Handle 1920×1080 and 3840×2160 correctly, relevant overscan/letterbox/safe-area behavior, and at least a sensible 16:10/ultrawide desktop fallback without broken navigation.
• Don't force an enormous ornamental handheld chassis/frame into the TV canvas. The content and navigational hierarchy should be primary, with restrained TrainerOS motifs.

Mode changes

Switching TV ↔ handheld when safe should preserve page, current selection, conversation, draft, party/call and game context. Prevent focus from falling onto stale/unmounted controls during layout swap.

During an active emulator, changing display/profile must preserve the owned game session; don't relaunch or break save/streaming/call lifecycle to redraw shell chrome.

Performance

Stay within existing Qt Quick/Gamescope constraints: prevent redundant expensive art decode, excessive Canvas redraw or scaling blur at 4K; use appropriate image resolution and sane animation/reduced-motion policy.

Acceptance

• At 1080p and 4K, TV mode renders a genuine redesigned hierarchy, not simply 960x540 × scale.
• Handheld 960×540 composition and performance do not regress.
• TV can be selected even when resolution does not meet a specific threshold; desktop/handheld can be forced on a high-resolution display.
• TV mode uses true safe-area and legible typography/focus from sofa distance.
• Dynamic resizing/external display switching restores focus and does not lose Trainer-owned app state.
• Shared services/controllers remain single implementations.
• Automated screenshots and an actual TV/controller check document the difference.

TV implementation tasks

• TV UX: redesign Home, libraries, OddCrate, Social and game overlays for couch viewing #157 — recompose Home, Worlds, Multiverse, OddCrate, Social, Trainer, Companions and modals for sofa viewing
• TV input UX: reliable D-pad/remote focus, text entry and accessibility at ten feet #158 — controller/remote navigation, keyboard/focus/accessibility
• TV display profiles: external screen, docked mode and safe transition without host takeover #159 — external-screen/dock profile selection, override, safe transitions
• Acceptance: independent image/software updates and true handheld/TV parity across install modes #160 — physical TV 1080p/4K versus handheld QA and update matrix

Shared controllers/data remain authoritative: #111 navigation, #113 reviews, #127–#135 Social/Together, #144–#152 OddCrate. Screen size or device name must not fork these backends.