docs(01-01): swap manifest permissions tabCapture->desktopCapture, drop alarms (D-A6/D-05)

Replace 'tabCapture' with 'desktopCapture' to match the new
getDisplayMedia capture path (D-A6). Remove 'alarms' because the
Phase 01 SW keepalive moves to a long-lived chrome.runtime.connect
port and the alarms code is deleted in Plan 05; declaring an unused
permission expands attack surface and is mitigated here per T-1-02.
activeTab is retained for chrome.tabs.captureVisibleTab in Phase 3,
and offscreen is retained for chrome.offscreen.createDocument.

manifest.json

@@ -4,12 +4,11 @@
   "version": "1.0.0",
   "description": "Запись сессий операторов для диагностики ошибок",
   "permissions": [
-    "tabCapture",
+    "desktopCapture",
     "activeTab",
     "downloads",
     "scripting",
     "storage",
-    "alarms",
     "offscreen"
   ],
   "host_permissions": [