Let the master dashboard drive this instance; drop the AutoBuyer switch

Three changes that ride together because they touch the same surface.

A control link to the master. lib/master-link.ts dials out to
<master>/ws/instance and holds it open, so the dashboard can trigger a trade or
queue an AutoBuyer run here. Commands call the same functions the local pages
call — runTrade, startScheduler, queueRun — so nothing reaches the broker by a
path the UI does not also use. Reports prefer the socket and fall back to the
existing POST, which keeps older masters working unchanged.

startMasterLink is idempotent, and that matters more than it looks: getClients()
is lazy and starts the link, so the first command re-enters it from inside a
command the live socket is waiting to ack. Tearing the socket down there loses
the ack and reports a trade that actually executed as a failure — which invites
pressing the button twice.

queueRun is lifted out of the automations route so the socket and HTTP share one
copy of the input clamping that decides how many times a purchase fires.

Page capture loses its switch and gains a scope. It now runs every tick, but
only against the active tab of the last-focused window that matches
host_permissions — so it follows the page in front of you and stops when you
switch away, where before it would fall back to any firm tab left open in the
background.

autobuyer_enabled is gone entirely. The AutoBuyer is ready whenever the runner
is; a run happens because someone asked for one. That does mean a queued run
executes as soon as clicker/runner.py claims it, with no second gate — stopping
the runner is now the way to make a machine idle.

Extension to 0.10.0; it needs a manual reload at chrome://extensions.

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

app/settings/page.tsx

@@ -201,7 +201,8 @@ export default function SettingsPage() {
                         <div>
                             <p className="text-sm font-medium text-slate-800">Dashboard URL</p>
                             <p className="text-xs text-slate-400 mt-0.5">
-                                Reports state to this URL every 30 seconds
+                                Reports state here every 30 seconds, and holds a control
+                                socket open so the dashboard can trigger trades and buys
                             </p>
                         </div>
                         <input