fix(selfbot): smooth VNC capture via keepalive + stop ffmpeg leak on stream end

The Go-Live broadcast looked badly choppy: video and scrolling stuttered while
the cursor stayed smooth. Root cause is TigerVNC: it only refreshes its
framebuffer while a VNC client is attached, but the broadcast reads that
framebuffer with x11grab (not as a VNC client). With no viewer attached the
captured screen idled at ~1.5 fps (measured 3/30 distinct frames); the cursor
looked smooth only because x11grab overlays the live cursor on every frame.

- Add a headless RFB keepalive (vnc-keepalive.ts) that stays connected for the
  life of the stream and requests incremental framebuffer updates at the stream
  framerate. SelfbotStreamer starts it on broadcast start and tears it down on
  stop/self-end. Measured 3/30 -> 57/60 distinct frames at 60 fps. Fail-open;
  authenticates with VNC_PASSWORD or the ~/.config/tigervnc/passwd file.
- Fix a resource leak: when the Go-Live ended on its own, only the active flag
  was cleared, leaving the x11grab->nvenc ffmpeg running forever (pinning a CPU
  core while no media was transmitted, with only the gateway TCP left and no UDP
  media). The self-end path now tears down capture, keepalive and voice like
  stop() does.
- Tests for both paths (self-end teardown; keepalive DES auth, port mapping,
  password resolution). Add @types/bun so bun:test typechecks; document the
  keepalive and recommended Chrome flags in README and .env.example.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

bot/scripts/stream-test/README.md

@@ -32,6 +32,25 @@ bun bot/scripts/stream-test/stream-hold.ts
 node bot/scripts/stream-test/scenario.mjs
 ```
 
+Recommended Chrome flags on the streamed display (avoids the "restore pages?"
+bubble after an unclean exit and keeps a single clean window):
+```
+google-chrome --remote-debugging-port=9222 --start-maximized \
+  --hide-crash-restore-bubble --disable-session-crashed-bubble \
+  --autoplay-policy=no-user-gesture-required <url>
+```
+
+## Smooth capture (VNC keepalive)
+TigerVNC only refreshes its framebuffer while a VNC client is attached. The
+Discord broadcast reads the framebuffer with `x11grab` (not as a VNC client), so
+with no viewer attached the captured screen idles at ~1.5 fps and the stream
+looks badly choppy while the cursor still moves smoothly (x11grab overlays the
+live cursor each frame). `SelfbotStreamer` fixes this automatically: it keeps a
+tiny headless RFB client (`vnc-keepalive.ts`) connected for the life of the
+stream, requesting incremental updates at the stream framerate. Measured: 3/30
+distinct frames without it, ~57/60 with it. The keepalive authenticates with
+`VNC_PASSWORD` (or the `~/.config/tigervnc/passwd` file) and is fail-open.
+
 ## A/B framerate/resolution
 Lower settings to compare what Discord actually delivers to viewers, e.g.:
 ```