feat(maestro): redesign web UI — token system, dark/light, a11y status

Rewrite styles.css as an OKLCH design-system: cool-slate neutrals with a
single committed signal-green for "alive" (running status, primary action,
focus, selection). Monospace becomes the UI typeface; dark is default with a
full light theme via tokens, OS-following with a persisted header toggle.

- catalog: pulsing wordmark, status-bar tally (N sessions / M live) + daemon
  chips, color-independent session status (pulsing dot for running, hollow
  ring + "exited" badge for dead), reveal-on-hover kill, three teaching
  empty states.
- attach: state pill (live/closed/error), framed dark xterm w/ green cursor.
- spawn: bottom-sheet/dialog form, mono inputs with green focus rings.
- a11y: AA contrast both themes, visible focus, prefers-reduced-motion paths,
  status never color-only.
- theme.ts: dark/light toggle + persistence; mock.ts: DEV-only review fixture
  (?mock / ?mock&spawn / ?theme=), tree-shaken from production builds.

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

web/src/attach.ts

@@ -34,7 +34,7 @@ export async function renderAttach(
   shell.innerHTML = `
     <header class="attach-header">
       <a class="btn btn-ghost back" href="#/" aria-label="Back to catalog">←</a>
-      <span class="attach-title" title="${sessionId}">${sessionId.slice(0, 8)}</span>
+      <span class="attach-title" title="${sessionId}">session <span class="sid">${sessionId.slice(0, 8)}</span></span>
       <span class="attach-state" data-state="connecting">connecting…</span>
     </header>
     <div class="attach-body"></div>
@@ -60,9 +60,13 @@ export async function renderAttach(
     fontSize: 13,
     convertEol: false,
     theme: {
-      background: "#101115",
-      foreground: "#e6e6e6",
-      cursor: "#e6e6e6",
+      // The terminal stays dark in both app themes (convention); colors are
+      // tuned to the maestro palette — signal-green cursor, slate background.
+      background: "#121419",
+      foreground: "#e6e8ec",
+      cursor: "#5fe3a1",
+      cursorAccent: "#121419",
+      selectionBackground: "#2b6b4f",
     },
     scrollback: 5000,
     allowProposedApi: true,