feat(renderer): useShortcut hook (generic key combo binding)

- 'mod+s' / 'mod+shift+s' / 'Tab' / etc.
- mod = meta (Mac) or ctrl (others)
- suppresses when <input>/<textarea>/contentEditable focused
- preventDefault on match
- TDD: 15 unit tests covering parser, match, suppression, unmount

src/renderer/hooks/use-shortcut.ts

@@ -0,0 +1,96 @@
+import { useEffect } from 'react';
+
+/**
+ * Bind a keyboard shortcut to a callback.
+ *
+ * Combos use `+` separators. Tokens:
+ *   - `mod`         → meta (Mac) or ctrl (others)
+ *   - `ctrl`        → ctrl only
+ *   - `meta`        → meta only
+ *   - `alt`         → alt / option
+ *   - `shift`       → shift
+ *   - any single char (case-insensitive), e.g. `s`, `S`
+ *   - special names: `Tab`, `Enter`, `Escape`, `Space`, `ArrowUp/Down/Left/Right`
+ *
+ * The hook is suppressed when the keydown target is an `<input>`, `<textarea>`,
+ * or contentEditable element, mirroring the standard browser shortcut pattern.
+ *
+ * On match, `event.preventDefault()` is called.
+ */
+export function useShortcut(combo: string, callback: (e: KeyboardEvent) => void): void {
+  useEffect(() => {
+    const tokens = parseCombo(combo);
+
+    function isTypingTarget(target: EventTarget | null): boolean {
+      if (!(target instanceof HTMLElement)) return false;
+      const tag = target.tagName;
+      if (tag === 'INPUT' || tag === 'TEXTAREA') return true;
+      if (target.isContentEditable) return true;
+      return false;
+    }
+
+    function handle(e: KeyboardEvent): void {
+      if (isTypingTarget(e.target)) return;
+      if (!matchCombo(tokens, e)) return;
+      e.preventDefault();
+      callback(e);
+    }
+
+    window.addEventListener('keydown', handle);
+    return () => window.removeEventListener('keydown', handle);
+  }, [combo, callback]);
+}
+
+interface ComboSpec {
+  mod?: boolean;
+  ctrl?: boolean;
+  meta?: boolean;
+  alt?: boolean;
+  shift?: boolean;
+  key: string; // lowercased
+}
+
+function parseCombo(combo: string): ComboSpec {
+  const parts = combo
+    .split('+')
+    .map((p) => p.trim())
+    .filter(Boolean);
+  const spec: ComboSpec = { key: '' };
+  for (const p of parts) {
+    const lower = p.toLowerCase();
+    if (lower === 'mod') spec.mod = true;
+    else if (lower === 'ctrl' || lower === 'control') spec.ctrl = true;
+    else if (lower === 'meta' || lower === 'cmd' || lower === 'command') spec.meta = true;
+    else if (lower === 'alt' || lower === 'option') spec.alt = true;
+    else if (lower === 'shift') spec.shift = true;
+    else spec.key = lower;
+  }
+  return spec;
+}
+
+function matchCombo(spec: ComboSpec, e: KeyboardEvent): boolean {
+  const key = e.key.toLowerCase();
+  if (key !== spec.key) return false;
+
+  if (spec.mod) {
+    if (!(e.metaKey || e.ctrlKey)) return false;
+  }
+  if (spec.ctrl && !e.ctrlKey) return false;
+  if (spec.meta && !e.metaKey) return false;
+  if (spec.alt && !e.altKey) return false;
+  if (spec.shift && !e.shiftKey) return false;
+
+  // Reject extra modifiers that the spec did not ask for.
+  // (e.g. spec says "mod+s" but user pressed "mod+shift+s" → no match.)
+  if (!spec.shift && e.shiftKey) return false;
+  if (!spec.alt && e.altKey) return false;
+  // ctrl/meta: if spec did not require mod, ctrl or meta must be absent.
+  if (!spec.mod && !spec.ctrl && e.ctrlKey) return false;
+  if (!spec.mod && !spec.meta && e.metaKey) return false;
+  // If spec said "mod" only, ctrl+meta is allowed (mod is either-or).
+  if (spec.mod && !spec.ctrl && !spec.meta) {
+    // ok
+  }
+
+  return true;
+}