refactor(stream-test): real-wheel into view, no synthetic-click fallback

Address review accuracy: humanClick used DOM scrollIntoViewIfNeeded and fell
back to Playwright locator.click() when an element had no box - neither is real
input. Now it brings elements into view with a real wheel scroll and throws if
there is no on-screen box (no synthetic click). Header comment and README
corrected: xdotool injects synthetic X input (not a physical HID device), and
all actions are real input while the CDP/DOM API is used only to read state.

bot/scripts/stream-test/README.md

@@ -8,13 +8,16 @@ real browsing session captured from the X display.
   until stopped. All params from `.env` (`DISCORD_SELFBOT_TOKEN`,
   `DISCORD_GUILD_ID`, `DISCORD_VOICE_CHANNEL_ID`, `VNC_RESOLUTION`,
   `VNC_FRAMERATE`, `VNC_BITRATE_KBPS`, `STREAM_HW`, `VNC_DISPLAY`).
-- `human.mjs` - human-like interaction helpers. Real mouse/keyboard via
-  `xdotool` (so the cursor is visible in the stream); Playwright only locates
-  elements. Every action is real input: address-bar navigation (Ctrl+L +
-  typing), search typing, clicking the video / settings menu / autoplay toggle /
-  play button, fullscreen via the `f` key, scrolling, and entering links. The
-  CDP/DOM API is used only to read state for verification, and as a rare click
-  fallback when an element has no on-screen box.
+- `human.mjs` - human-like interaction helpers. Input is injected into the X
+  server with `xdotool` (synthetic X input, not a physical HID device, but the
+  browser and the captured screen see genuine pointer/keyboard events with a
+  visibly moving cursor); Playwright only locates elements. Every action is such
+  input: address-bar navigation (Ctrl+L + typing), search typing, clicking the
+  video / settings menu / autoplay toggle / play button, fullscreen via the `f`
+  key, and scrolling. Elements are brought into view with a real wheel scroll
+  (no DOM scrollIntoView); if an element has no on-screen box the click fails
+  rather than falling back to a synthetic click. The CDP/DOM API is used only to
+  read state for verification, never to act.
 - `scenario.mjs` - the browse scenario (YouTube -> IU live -> 1080p ->
   fullscreen -> Naver -> 나무위키), driven with the human helpers. Connects to a
   Chrome already running with `--remote-debugging-port` (`CDP_PORT`, default