fix(ws): re-attach stateChange listeners when bot instance is replaced

startBot creates a fresh BotInstance but the WS layer keyed its listener
map by bot.id, so ensureAllBotsAttached skipped the new object and
stateChange events were never broadcast — the player bar only appeared
after a manual refresh. BotManager now extends EventEmitter and emits
"botInstance" whenever a new bot object is created; websocket.ts stores
the bot reference, detaches on replacement, and subscribes to the event
for immediate wiring.

Also enlarges the bot selector (padding 10×20, font 16, min-height 44,
bigger dot/chevron/state icons, wider name) and adds Playwright repro
scripts for the player bar bug and navbar sizing check.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/screenshot_navbar.py

@@ -0,0 +1,12 @@
+from playwright.sync_api import sync_playwright
+
+with sync_playwright() as p:
+    browser = p.chromium.launch(headless=True)
+    page = browser.new_page(viewport={"width": 1440, "height": 900})
+    page.goto("http://localhost:3000")
+    page.wait_for_load_state("networkidle")
+    page.wait_for_timeout(800)
+    page.locator(".navbar").screenshot(path="scripts/navbar_bigger.png")
+    rect = page.locator(".bot-selector-btn").bounding_box()
+    print("bot-selector-btn bbox:", rect)
+    browser.close()