feat(maestro): add the web ctrl-k command bar

The overlay, the query line and the session half of the results
(docs/COMMAND-BAR.md): an empty query lists sessions most recently
focused first, typing ranks through `matchAndRank` with the winning
field's ranges highlighted, and results render under kind headers
ordered by their best-scoring member.

Enter dispatches `SESSION_SELECT_EVENT`, the path the sidebar's click
and the hash router already share, so a bar attach cannot leave the
layout in a state a click could not produce.

The global key listener moves to the capture phase, which #148 left
alone: an attached xterm swallows every keystroke it is given, so
ctrl-k has to be seen ahead of the terminal.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/styles.css

@@ -1425,6 +1425,128 @@ input.leaf-rename:focus {
   color: var(--muted);
 }
 
+/* ---------- command bar (Ctrl+K) — docs/COMMAND-BAR.md ---------- */
+/* Same family of surface as the spawn modal and the help overlay: the overlay
+   tokens below are theirs, not a third set. */
+.cmdbar-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: var(--z-modal);
+  display: grid;
+  grid-template-rows: 12vh auto 1fr;
+  justify-items: center;
+  padding: var(--sp-4);
+  background: oklch(0 0 0 / 0.5);
+  backdrop-filter: blur(4px);
+}
+
+.cmdbar-panel {
+  grid-row: 2;
+  display: flex;
+  flex-direction: column;
+  width: min(560px, 100%);
+  max-height: min(60vh, 520px);
+  overflow: hidden;
+  background: var(--surface);
+  border: 1px solid var(--border-strong);
+  border-radius: var(--r-3);
+  box-shadow: var(--shadow-2);
+}
+
+.cmdbar-input {
+  appearance: none;
+  background: none;
+  border: 0;
+  border-bottom: 1px solid var(--border);
+  border-radius: 0;
+  color: var(--ink);
+  font-family: var(--font-mono);
+  font-size: var(--fs-15);
+  padding: var(--sp-3) var(--sp-4);
+}
+
+.cmdbar-input:focus-visible {
+  outline: none;
+}
+
+.cmdbar-results {
+  overflow-y: auto;
+  padding: var(--sp-2) 0;
+}
+
+.cmdbar-group-title {
+  padding: var(--sp-2) var(--sp-4) var(--sp-1);
+  font-size: var(--fs-11);
+  font-weight: 600;
+  letter-spacing: 0.08em;
+  text-transform: uppercase;
+  color: var(--faint);
+}
+
+.cmdbar-row {
+  display: flex;
+  align-items: baseline;
+  gap: var(--sp-3);
+  padding: var(--sp-1) var(--sp-4);
+  cursor: pointer;
+}
+
+.cmdbar-row.is-active {
+  background: var(--surface-3);
+}
+
+.cmdbar-row-name {
+  font-size: var(--fs-13);
+  color: var(--ink);
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+/* A dead session still lists — it just is not where you just were. */
+.cmdbar-row.is-dead .cmdbar-row-name {
+  color: var(--muted);
+}
+
+.cmdbar-row-meta {
+  flex: 1 1 auto;
+  min-width: 0;
+  font-size: var(--fs-11);
+  color: var(--faint);
+  text-align: right;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.cmdbar-hit {
+  background: none;
+  color: var(--accent);
+  font-weight: 600;
+}
+
+.cmdbar-empty {
+  padding: var(--sp-3) var(--sp-4);
+  font-size: var(--fs-13);
+  color: var(--muted);
+}
+
+/* Phone: the bottom-sheet treatment the spawn modal already uses. */
+@media (max-width: 600px) {
+  .cmdbar-overlay {
+    grid-template-rows: 1fr auto;
+    padding: 0;
+  }
+
+  .cmdbar-panel {
+    grid-row: 2;
+    width: 100%;
+    max-height: 70vh;
+    border-radius: var(--r-3) var(--r-3) 0 0;
+    border-bottom: 0;
+  }
+}
+
 /* Line 2 — dot + duration in the state's colour, then muted fragments. The
    state word itself is never spelled out here; the colour carries it. */
 .card-line2 {