feat(remote): host-unreachable banner, manual wake, and native MAC wake-on-LAN

The reactive wake (typing into a session whose host slept) left the state invisible:
nothing told the user the machine was asleep, and with no wake target configured
there was nothing to do about it. Adds:

- RemoteHost.wakeMac (comma-separated) - Codeman builds and broadcasts the magic
  packet itself (UDP port 9), so the common case needs no external script. The
  existing wakeCommand stays as the explicit override.
- GET /api/sessions/:id/reachability - probes (throttled, cached, and it never
  wakes) and reports HOW the host can be woken, or that nothing is configured.
- POST /api/sessions/:id/wake - wakes, waits, reattaches the pane and flushes
  buffered input; 400 with a routable message when no target is configured.
- The amber host-unreachable banner + its 'Wake' / 'Configure WoL' action, and a
  small config dialog that saves via PUT /api/remote-hosts/:id.
- RemoteWakeDeps.resolveRemote: host config is re-resolved for LIVE sessions
  (throttled + cached), so saving the dialog takes effect without a restart.

src/web/public/session-ui.js

@@ -3071,6 +3071,9 @@ Object.assign(CodemanApp.prototype, {
     const identityFile = document.getElementById('remoteHostIdentityFile').value.trim();
     const socksProxy = document.getElementById('remoteHostSocksProxy').value.trim();
     const jumpHost = document.getElementById('remoteHostJumpHost').value.trim();
+    // Wake-on-LAN: keep in sync with `_readRemoteHostFromForm` (the Discover path).
+    const wakeMac = document.getElementById('remoteHostWakeMac').value.trim();
+    const wakeCommand = document.getElementById('remoteHostWakeCommand').value.trim();
     const extraSshOptions = document.getElementById('remoteHostExtraSshOptions').value
       .split('\n')
       .map(line => line.trim())
@@ -3108,6 +3111,8 @@ Object.assign(CodemanApp.prototype, {
         ...(socksProxy ? { socksProxy } : {}),
         ...(jumpHost ? { jumpHost } : {}),
         ...(extraSshOptions.length ? { extraSshOptions } : {}),
+        ...(wakeMac ? { wakeMac } : {}),
+        ...(wakeCommand ? { wakeCommand } : {}),
         ...(codexCommand ? { commands: { codex: codexCommand } } : {}),
       };
       const hostRes = await fetch('/api/remote-hosts', {
@@ -3568,6 +3573,9 @@ Object.assign(CodemanApp.prototype, {
     const socksProxy = document.getElementById('remoteHostSocksProxy').value.trim();
     const jumpHost = document.getElementById('remoteHostJumpHost').value.trim();
     const codexCommand = document.getElementById('remoteHostCodexCommand').value.trim();
+    // Wake-on-LAN: keep in sync with `linkRemoteCase`'s inline payload.
+    const wakeMac = document.getElementById('remoteHostWakeMac').value.trim();
+    const wakeCommand = document.getElementById('remoteHostWakeCommand').value.trim();
     const extraSshOptions = document.getElementById('remoteHostExtraSshOptions').value
       .split('\n')
       .map(line => line.trim())
@@ -3587,6 +3595,8 @@ Object.assign(CodemanApp.prototype, {
       ...(socksProxy ? { socksProxy } : {}),
       ...(jumpHost ? { jumpHost } : {}),
       ...(extraSshOptions.length ? { extraSshOptions } : {}),
+      ...(wakeMac ? { wakeMac } : {}),
+      ...(wakeCommand ? { wakeCommand } : {}),
       ...(codexCommand ? { commands: { codex: codexCommand } } : {}),
     };
   },