fix: v2.0.1 release — fix broken installs, CI, security, and docs

Critical fixes:
- npm postinstall.js: BINARY_VERSION '1.1.3' → '2.0.1' (every install was 404ing)
- npm package name: corrected error messages to 'vestige-mcp-server'
- README: npm install command pointed to wrong package
- MSRV: bumped from 1.85 to 1.91 (uses floor_char_boundary from 1.91)
- CI: removed stale 'develop' branch from test.yml triggers

Security hardening:
- CSP: restricted connect-src from wildcard 'ws: wss:' to localhost-only
- Added X-Frame-Options, X-Content-Type-Options, Referrer-Policy, Permissions-Policy headers
- Added frame-ancestors 'none', base-uri 'self', form-action 'self' to CSP
- Capped retention_distribution endpoint from 10k to 1k nodes
- Added debug logging for WebSocket connections without Origin header

Maintenance:
- All clippy warnings fixed (58 total: redundant closures, collapsible ifs, no-op casts)
- All versions harmonized to 2.0.1 across Cargo.toml and package.json
- CLAUDE.md updated to match v2.0.1 (21 tools, 29 modules, 1238 tests)
- docs/CLAUDE-SETUP.md updated deprecated function names
- License corrected to AGPL-3.0-only in root package.json

1,238 tests passing, 0 clippy warnings.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/vestige-core/src/fsrs/scheduler.rs

@@ -241,17 +241,15 @@ impl FSRSScheduler {
         };
 
         // Apply sentiment boost
-        if self.enable_sentiment_boost {
-            if let Some(sentiment) = sentiment_boost {
-                if sentiment > 0.0 {
+        if self.enable_sentiment_boost
+            && let Some(sentiment) = sentiment_boost
+                && sentiment > 0.0 {
                     new_state.stability = apply_sentiment_boost(
                         new_state.stability,
                         sentiment,
                         self.max_sentiment_boost,
                     );
                 }
-            }
-        }
 
         let mut interval =
             next_interval_with_decay(new_state.stability, self.params.desired_retention, w20)