Document Windows support and the AutoBuyer components

focus.py now verifies on Windows rather than assuming activation worked. Windows
declines to raise a window for a process that doesn't own the foreground — it
flashes the taskbar and the call returns as if it succeeded — so the runner reads
the foreground window's process back and reports a failure instead of clicking
into a background window. Same gap that was fixed on macOS earlier.

The runner also declares itself DPI-aware at startup. Without it Windows reports
a virtualised screen size and rescales the coordinates it accepts, while the
browser keeps reporting CSS pixels; on a display at 125% or 150% the two disagree
and clicks drift further off the further they are from the top-left.

Browser windows are matched on the owning process rather than the window title, so
an editor with chrome.js open is no longer mistaken for the browser. Linux now says
window management is unsupported there, rather than reporting no browser found —
pygetwindow has no X11 backend, and "no browser window" reads like Chrome is shut.

The main README gained a section on the AutoBuyer: what the three pieces are, how
to load the extension, and that neither the extension nor the runner reloads
itself when the source changes. That last point has been the cause of most of the
confusing failures so far, so it is called out in Updating too.

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

README.md

@@ -91,6 +91,67 @@ Open the app in your browser and add your firms through the UI:
 
 ---
 
+## AutoBuyer (browser automation)
+
+The AutoBuyer page drives a real browser to buy and reset prop-firm accounts. It
+is three pieces, and all three must be running:
+
+| Piece | What it does |
+|---|---|
+| the dashboard | Defines automations, queues runs, shows progress |
+| `extension/` | A Chromium extension that reads the broker page and measures elements |
+| `clicker/runner.py` | A desktop process that moves the real mouse and keyboard |
+
+Automations are declared in `lib/automations.ts` — one entry per firm, with the
+steps inside. Adding a button means editing that file; the page and the runner
+pick it up from the server.
+
+### 1. Load the extension
+
+`chrome://extensions` → enable **Developer mode** → **Load unpacked** →
+select the `extension` folder.
+
+Chrome does **not** reload an unpacked extension when its files change. After
+pulling updates, click the reload icon on its card — the dashboard shows the
+version it sees, and a mismatch means the reload did not take.
+
+Adding a new firm also means adding its host to `host_permissions` in
+`extension/manifest.json` and reloading. Without it the extension cannot read
+that site, and every step fails to locate.
+
+### 2. Install the clicker
+
+```powershell
+cd clicker
+pip install -r requirements.txt
+```
+
+See `clicker/README.md` for the per-platform notes — display scaling and
+foreground lock both matter on Windows — and for the verification sequence to
+run before letting it click anything on a new machine.
+
+### 3. Start the runner
+
+```powershell
+python clicker\runner.py
+```
+
+Leave it running. It reports in every two seconds, and the dashboard greys out
+the automation buttons when it is not there. A running Python process does not
+reload when the source changes, so restart it after pulling updates; the
+dashboard warns when its version is behind.
+
+### Running it
+
+Turn **Page capture** on from the AutoBuyer page, then press an automation's
+button. Progress appears per step, and **Stop** halts a run between steps.
+
+The browser must be visible and frontmost while a run is in flight — the clicks
+are real OS-level input, so the machine cannot be used for anything else, and a
+dialog stealing focus fails the step. That makes an RDP session a poor host:
+disconnecting can suspend the desktop and break clicks in ways that are hard to
+diagnose.
+
 ## Keeping it running (PM2)
 
 Install PM2 globally:
@@ -119,6 +180,15 @@ npm run build
 pm2 restart autofirmer
 ```
 
+If the update touched the AutoBuyer, two things do **not** reload themselves:
+
+- **The extension** — click reload on its card in `chrome://extensions`.
+- **The runner** — stop it with Ctrl-C and start it again.
+
+The dashboard reports the version it sees from each, and warns when either is
+behind. Most AutoBuyer bugs that look mysterious are one of these two still
+running the previous code.
+
 ---
 
 ## Firewall
@@ -146,3 +216,12 @@ npm install       # only needed if dependencies changed
 npm run build
 pm2 restart autofirmer
 ```
+
+If the update touched the AutoBuyer, two things do **not** reload themselves:
+
+- **The extension** — click reload on its card in `chrome://extensions`.
+- **The runner** — stop it with Ctrl-C and start it again.
+
+The dashboard reports the version it sees from each, and warns when either is
+behind. Most AutoBuyer bugs that look mysterious are one of these two still
+running the previous code.