fix: isInNonChatArea too aggressive — blocking reveal on chat content

The class-based selectors ([class*="header"], [class*="Header"],
[class*="nav-"], etc.) were matching Claude.ai's chat content area
elements, preventing reveal from running on any response text.

Narrowed to only structural elements: nav, aside, [role="navigation"],
[role="complementary"], [data-sidebar]. Removed HEADER/FOOTER from
SKIP_REVEAL_TAGS since sites use these tags inside chat layouts.

https://claude.ai/code/session_01KF4i7Ra7zCEDskxDBaNtcT

manifest.firefox.json

@@ -1,7 +1,7 @@
 {
   "manifest_version": 3,
   "name": "Silent Send",
-  "version": "0.9.16",
+  "version": "0.9.17",
   "description": "Intercepts personal info and substitutes it with user-defined replacements before sending to AI services.",
   "browser_specific_settings": {
     "gecko": {