fix: keyboard round 3 — question walk clamps, Tab focus toggle, Alt+arrow isolation, search Esc

Owner live-test rounds on waves A/B:
- Alt+arrows no longer ALSO walk the question rows (dock ignores
  alt/meta/ctrl combos; session cycling keeps them exclusively)
- question walk clamps at the ends — no wrap (faster to navigate)
- plain Tab toggles focus between the thinking field and the answer
  rows (walked row by default); focus follows the walk while in the
  rows; Shift+Tab stays the global thinking-level cycle
- Esc in the sessions search blurs back to normal (claims the key so
  the window Esc chain does not fire)
- cheat sheet gains the Tab-in-question display entry

components/sidebar.tsx

@@ -436,6 +436,15 @@ function SessionsSidebar() {
 							data-testid="session-search"
 							value={query}
 							onChange={(e) => setQuery(e.target.value)}
+							// Esc leaves the search (owner, keyboard wave): blur back
+							// to normal, and claim the key so the window Esc chain
+							// (dictation / abort) doesn't also fire.
+							onKeyDown={(e) => {
+								if (e.key === "Escape") {
+									e.stopPropagation();
+									e.currentTarget.blur();
+								}
+							}}
 							placeholder="Search..."
 							aria-label="Search sessions"
 							className="h-6 rounded-sm border-border bg-background pl-6 text-xs placeholder:text-muted-foreground/60"