Fix 15 pre-existing ESLint issues in studyPages.tsx; v2.1.1

Fixes two real bugs: useEffect and usePageMeta were called after an early
"study not found" return, violating React's rules of hooks (could corrupt
hook state if a study slug resolves inconsistently across renders). Also
removes dead code (unused NOTE_ANCHORS array, an unused state pair, a stale
eslint-disable comment), fixes three return-in-finally statements that could
mask exceptions, adds the missing study?.slug effect dependency, and cleans
up an unnecessary regex escape and an empty catch block.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "siteforge",
   "private": true,
-  "version": "2.1.0",
+  "version": "2.1.1",
   "type": "module",
   "scripts": {
     "dev": "vite",