phase36(display-engine): polish row UX and dynamic state boundary

[MarsDoge]

Summary

Phase36 expands the Modern DisplayEngine row-polish branch from the initial FormModel row accent slice into a coherent DisplayEngine UX/data-boundary batch.

This keeps edk2 FormBrowser as the owner of HII/IFR/ConfigAccess semantics and keeps Modern DisplayEngine focused on rendering already-materialized state.

UX / rendering

• Adds FormModel-driven row accents for statement kind/state.
• Adds text inset for native FormBrowser prompt/value glyphs inside modern rows.
• Adds a subtle right-rail divider between actionable rows and contextual help.
• Surfaces page state through footer status text/chips:
  • LIVE VIEW
  • LIVE REFRESH
  • UNSAVED CHANGES
  • REBOOT REQUIRED reserved state
  • MODAL VIEW
• Adds a highlighted value lane to make prompt/value separation clearer.
• Reserves footer hotkey text space for the status chip.
• Shows seconds in header time so redraw/refresh activity has visible feedback.

Dynamic data / config boundary

• Adds English + zh-CN docs for the intended PEI -> DXE services -> ModernSetupApp/DisplayEngine pipeline.
• Documents that DisplayEngine may render live/refresh/unsaved/reboot-required affordances but must not own hardware probing, policy decisions, or storage writes.
• Adds smoke coverage to guard against DisplayEngine renderer ownership of hardware/config mutation tokens.

Files

• Library/ModernUiCustomizedDisplayLib/CustomizedDisplayLibInternal.c
• Library/ModernUiEngineLib/ModernUiEngineLib.c
• Docs/DisplayEngineDynamicDataFlow.md
• Docs/DisplayEngineDynamicDataFlow.zh-CN.md
• Tests/Smoke/smoke_validate.py
• CHANGELOG.md

Validation

• python3 Tests/Smoke/smoke_validate.py
• git diff --check
• TARGET=RELEASE MODERN_SETUP_DISPLAY_ENGINE=modern MODERN_SETUP_REPLACE_UIAPP=1 Scripts/build-ovmf-x64.sh
• Scripts/xarch-validate.sh --all --mode dry-run
• DisplayEngine OVMF X64 capture sanity

Capture evidence root:

/tmp/modernsetup-phase36-batch-capture-20260523205754

Captured images:

/tmp/modernsetup-phase36-batch-capture-20260523205754/native/displayengine-ovmf-x64-native.png
/tmp/modernsetup-phase36-batch-capture-20260523205754/modern/displayengine-ovmf-x64-modern.png

Visual sanity:

• Native baseline capture: non-empty OVMF EFI Firmware Setup/FormBrowser page; not boot selector, blank, or crash.
• Modern capture: non-empty OVMF EFI Firmware Setup/FormBrowser page; not boot selector, blank, or crash.
• Modern capture visibly shows the dark/orange DisplayEngine treatment, modern row surface/highlight, right-side contextual help region, and footer hotkey area.
• Header seconds/status chip are implemented and build/smoke covered, but this specific front-page capture does not clearly expose every status/chrome affordance.

Boundary notes

This PR intentionally does not add:

• DisplayEngine-owned SetVariable
• RouteConfig / ExtractConfig
• HiiSetBrowserData
• ConfigAccess
• direct hardware probing
• native DisplayEngine UX changes

REBOOT REQUIRED is a reserved display state only. It is not inferred from generic unsaved state until a real platform/FormBrowser source is wired.