feat(window): add vim-style directional window moves

[fcoury-oai]

Why

The existing Ctrl-w h/j/k/l bindings only change focus, so there is no Vim-compatible way to physically reposition the active split. Recreating a window to simulate movement would also lose stable window identity, viewport state, attached window bars, and unrelated split ratios.

What Changed

• Add Ctrl-w H/J/K/L to move the active split to the full-height left/right or full-width top/bottom edge while keeping lowercase focus navigation unchanged.
• Restructure the split tree without replacing the active window, preserving stable IDs, cursors, viewports, existing split ratios, session snapshots, and sidebar-reserved geometry.
• Compare every window position and size when refreshing plugin snapshots so layout changes are delivered without incorrect window-close or focus events.
• Add command-palette entries, prefix hints, documentation, legacy-configuration coverage, and unit and integration regressions.

How to Test

1. Start Red, open a vertical split with Ctrl-w v, then a horizontal split with Ctrl-w s; open a different file in each pane.
2. Press Ctrl-w H, Ctrl-w J, Ctrl-w K, and Ctrl-w L. Verify the active file moves to the full left, bottom, top, and right edge, remains focused, and retains its cursor.
3. Open Neo-tree with Ctrl-e, repeat a window move, and verify the sidebar remains visible and the editor panes stay inside the reserved area.
4. Verify lowercase Ctrl-w h/j/k/l still only changes focus. Repeat a move toward an already occupied outer edge and confirm it is a silent no-op.
5. Run cargo test --lib window and cargo test --test editing --quiet to exercise stable IDs, plugins, recovery, real shifted key events, legacy keymaps, and side panels.

Validation

• cargo test --all-features --quiet — 1,588 passing tests.
• cargo clippy --all-targets --all-features -- -D warnings.
• cargo fmt --all -- --check.
• Interactive tmux smoke test for all four edge moves and Neo-tree.