feat(maestro): terminal-native web UI pass + design kit

Live-review iteration on the browser SPA, driven by crit feedback.

Sidebar / session tree
- Compact single-line leaf rows; status shown as a faint "alive" row wash
  instead of per-row dots (exited rows dim + keep the "exited" badge).
- Host is now the first level of nesting (host → label path → session); the
  inline @daemon is dropped from rows.
- Flush, borderless search input spanning the sidebar; drag-to-resize grip on
  the sidebar edge (width persisted to localStorage); narrower default.
- Per-row clone action (opens the spawn modal prefilled); right-pointing
  chevron when collapsed.

Chrome / layout
- Buttons swapped to a bracket terminal style ([ + Spawn ]); ghost/icon drop
  the brackets. Old filled styles removed.
- Squared corners globally (radius tokens) and tighter, denser spacing.
- Session tally + daemon chips moved into the centered app header.
- Shorter control height; shared --bar-h aligns the search and attach bars.

Attach / terminal
- Useful attach title (name · command @ host) over a bare UUID.
- Robust fit: compute columns from the viewport's scrollbar-excluded
  clientWidth (fixes mobile under-fit and desktop overflow); ResizeObserver +
  font-load refit; full-bleed terminal on mobile.

Spawn / empty states
- Spawn modal accepts a prefill (clone); real "+ Spawn" buttons in welcome and
  no-sessions empty states.

Dev
- New ?kit design-kit page (kit.ts/kit.css, DEV-only) showcasing components.
- Richer ?mock fixture with deeper label nesting.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/spawn.ts

@@ -2,7 +2,20 @@ import { createSession } from "./api.js";
 import { attachDirAutocomplete } from "./dirAutocomplete.js";
 import type { CreateSessionRequest, DaemonInfo } from "./types.js";
 
-export function openSpawnModal(daemons: Map<string, DaemonInfo>): void {
+/** Seed values for the spawn form — used by "clone" to reopen the dialog with
+ * the same daemon, cwd, command, name, and label as an existing session. */
+export interface SpawnPrefill {
+  daemon_id?: string;
+  cwd?: string;
+  command?: string;
+  name?: string;
+  label?: string;
+}
+
+export function openSpawnModal(
+  daemons: Map<string, DaemonInfo>,
+  prefill?: SpawnPrefill,
+): void {
   const existing = document.getElementById("modal-host");
   if (existing) existing.remove();
 
@@ -98,6 +111,30 @@ export function openSpawnModal(daemons: Map<string, DaemonInfo>): void {
   select.addEventListener("change", applyHomeDir);
   applyHomeDir();
 
+  // Clone: seed the form from an existing session. cwd is marked edited so the
+  // home-dir sync won't clobber it on daemon change.
+  if (prefill) {
+    (host.querySelector("#spawn-title") as HTMLElement).textContent =
+      "Clone session";
+    const set = (name: string, value: string | undefined) => {
+      if (value == null) return;
+      const field = host.querySelector(
+        `[name=${name}]`,
+      ) as HTMLInputElement | HTMLSelectElement | null;
+      if (field) field.value = value;
+    };
+    if (prefill.daemon_id && daemons.has(prefill.daemon_id)) {
+      select.value = prefill.daemon_id;
+    }
+    set("command", prefill.command);
+    set("name", prefill.name);
+    set("label", prefill.label);
+    if (prefill.cwd) {
+      cwdInput.value = prefill.cwd;
+      cwdEdited = true;
+    }
+  }
+
   // Live directory autocomplete (NAP-329) on the path fields, scoped to the
   // currently-selected daemon — re-reading `select.value` per query means it
   // tracks host changes for free.