Closes out the T-403 cross-pane vim layer. gt/gT bind to the existing
workspace.tab.next/previous commands (also on ctrl+pagedown/up for every
preset), resolved by the focused editor's matcher or a pane's PaneKeyNav —
bare-g sequences stay editor/pane-local (T-404's global matcher only engages
on modified-chord prefixes), so no global-matcher surgery.
- vim.yaml: g t -> command:workspace.tab.next, g shift+t -> .previous
(vim.normal); shares the `g` prefix with `g g` (docStart / nav.top),
distinguished by the final chord.
- PaneKeyNav now EXECUTES non-editor.vim.* command intents (e.g.
workspace.tab.*) instead of swallowing all command intents, so gt/gT work
from a focused pane; editor.vim.* buffer edits stay blocked in panes.
Tests: vim-preset resolution (gt/gT bind, gg intact), PaneKeyNav executes
the command from a pane, and editor.vim.* is never run from a pane. make
test green; analyze + format clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>