feat(app-core): table cells support the same inline formatting shortcuts as the editor

[junereycasuga]

What changed

Table cells now support the same inline formatting shortcuts as the main editor:

• Mod+B → bold **
• Mod+I → italic *
• Mod+E → code `
• Mod+K → link [...](...)
• Shift+Mod+S → strikethrough ~~
• Shift+Mod+H → highlight ==
• Shift+Mod+M → math $

The shortcuts work in both normal contenteditable cells and Vim visual-mode cells.

How it works

• cm-format.ts now exposes pure-text helpers toggleWrapEdit and wrapLinkEdit, which compute the same wrap/unwrap logic used by the editor.
• cm-table.ts applies those helpers directly to the cell source and updates the cell caret.
• VimNav now returns early when focus is inside a .cm-table-widget, so the global editor-level formatting chords don’t steal the shortcut from the cell.

Tests

Added coverage for all seven shortcuts in table cells, plus a Vim visual-selection + Mod+B case.

Verification

• npx vitest run src/lib/cm-format.test.ts src/lib/cm-table.test.ts — 78/78 tests pass
• npx tsc --noEmit -p tsconfig.json — clean