Improve home split-view behavior, auto two-column layout, and fragment replace with caching

[ZL114514]

Motivation

• Automatically adapt the home feed layout to larger widths so items become two columns when appropriate.
• Make split (two-pane) usage more ergonomic by keeping the home pane resident and routing comment/detail pages to the secondary pane.
• Replace fragment add transactions with replace while preserving UI state to avoid reloading Lua views on navigation.

Description

• Add updateHomeRecommendColumns and an OnLayoutChangeListener in layout/home.lua to compute and set the GridLayoutManager span count from the actual laid-out width and post an initial update.
• Resize and toggle visibility of left/right fragment containers in home.lua updateSekai so f1 (home) and f2 (secondary) get explicit widths in split mode.
• Implement selectTargetContainer and helper functions in mods/muk.lua, enable t.setReorderingAllowed(true), and change fragment transactions from t.add(...) to t.replace(...) so new fragments are placed into the chosen container.
• Add a simple container-view cache using MyFragmentViewmodel and update MyLuaFileFragment to store/restore the Lua fragment content view across view destruction/creation by setting mVM.cachedContentView and mVM.luaFileLoaded, and avoid re-running Lua file when cached view is reused.

Testing

• Ran git diff --check to ensure no trailing-whitespace issues (passed).
• Attempted ./gradlew :app:compileDebugJavaWithJavac but the build failed in this environment with Unsupported class file major version 69, which is a tooling/JDK mismatch and not related to the code changes.

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Codex Task