Add keyboard shortcuts

[iamnoksio]

Enable keyboard row navigation and shift-range selection in the file explorer, plus terminal font zoom shortcuts.

• ExplorerFileTable: handle ArrowUp/ArrowDown to move focus between rows, support Shift+Arrow for range selection, scroll focused row into view, and update selection state. Also tidy aria-sort/JSX formatting and minor data-entry-perms/size rendering adjustments.
• AppShell: introduce preZoomFontSizeRef and add Meta+=, Meta+-, Meta+0 shortcuts to increase, decrease, and reset terminal font size (active only on terminal tabs).

Close #104

Greptile Summary

This PR adds two keyboard-shortcut features: row-level Arrow navigation and Shift+Arrow range selection in the file explorer, and Meta+= / Meta+- / Meta+0 terminal font zoom shortcuts in the app shell. It also memoises sortedEntries and the derived sortedIds array to avoid rebuilding them on every keypress.

• ExplorerFileTable: Arrow key navigation walks the sorted row list with DOM-sibling focus/scroll; Shift+Arrow builds a range selection anchored at lastClickedId; sortedEntries and sortedIds are wrapped in useMemo; additional changes are formatting-only.
• AppShell: A preZoomFontSizeRef stores the font size before the first zoom step so Meta+0 can restore it; the ref is initialised to null and Meta+0 exits early when no zoom session is active, addressing a previous issue where it would hard-code 14 as the reset value.

Confidence Score: 5/5

Safe to merge; both feature areas are well-scoped and the previously reported regressions are resolved.

The keyboard navigation in the file explorer is straightforward DOM-sibling walking with a correctly memoised ID list. The font-zoom logic guards the pre-zoom ref properly and exits early on Meta+0 when nothing is zoomed. The two remaining observations (Cmd++ not covered, stale baseline on mid-session Settings change) are edge-case UX gaps rather than data-loss or crash conditions.

Files Needing Attention: AppShell.tsx — the zoom-baseline ref is the only place that could produce a surprising font-size reset.

Important Files Changed

Filename	Overview
src/components/layout/AppShell.tsx	Introduces terminal font zoom shortcuts (Meta+=/−/0) with a stable preZoomFontSizeRef; previous Meta+0 regression addressed. Minor: external Settings changes during an active zoom session will cause Meta+0 to restore a stale pre-zoom baseline rather than the user's updated configured value.
src/components/explorer/ExplorerFileTable.tsx	Adds ArrowUp/Down keyboard navigation and Shift+Arrow range selection for file rows, with DOM-sibling focus traversal and scrollIntoView. sortedEntries and sortedIds are properly memoised. Formatting-only changes to JSX and sort helpers are clean.

Sequence Diagram

sequenceDiagram
    participant User
    participant KeyboardHandler as useKeyboardShortcuts
    participant AppShell
    participant SettingsStore

    Note over User,SettingsStore: Terminal Font Zoom (AppShell)
    User->>KeyboardHandler: "Meta+="
    KeyboardHandler->>AppShell: action()
    AppShell->>SettingsStore: getState().terminalFontSize
    AppShell->>AppShell: "preZoomFontSizeRef.current = fontSize (if null)"
    AppShell->>SettingsStore: setTerminalFontSize(fontSize + 1)

    User->>KeyboardHandler: Meta+0
    KeyboardHandler->>AppShell: action()
    AppShell->>AppShell: "if preZoomFontSizeRef.current === null return"
    AppShell->>SettingsStore: setTerminalFontSize(preZoomFontSizeRef.current)
    AppShell->>AppShell: "preZoomFontSizeRef.current = null"

    Note over User,SettingsStore: Explorer Arrow Navigation (ExplorerFileTable)
    User->>KeyboardHandler: ArrowDown / ArrowUp (on row)
    KeyboardHandler->>KeyboardHandler: lookup nextIdx in sortedIds
    alt no Shift
        KeyboardHandler->>KeyboardHandler: setSelectedIds(nextId)
        KeyboardHandler->>KeyboardHandler: "lastClickedId = nextId"
    else Shift held
        KeyboardHandler->>KeyboardHandler: "anchor = lastClickedId or entry.id"
        KeyboardHandler->>KeyboardHandler: setSelectedIds(range anchor to next)
    end
    KeyboardHandler->>KeyboardHandler: nextRow.focus() + scrollIntoView()

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_{Reviews (3): Last reviewed commit: "fix: address review — safe Meta+0 reset ..." | Re-trigger Greptile}