chore: upgrade StudioBridge v2.1.2 -> v2.1.3, add persistent-folder creation, update runbook

- Rebuild StudioBridge-2.1.3.jar from latest upstream (v2.1.3) and deploy to portable-dist
- Add ensurePersistentDirectories() so the app creates ~/.studio-bridge and Profiles at startup (GUI + --sendonly)
- Bundle full StudioBridge source under StudioBridge-src/ (with rebuild-jar.bat)
- Update launchers (Launch-StudioBridge.bat, portable-dist/StudioBridge.bat) to v2.1.3
- Add check-update.ps1 and UPDATE.md for the step-by-step update runbook
- Update README (v2.1.3, persistent data + updating sections)
- Ignore StudioBridge-src/target/ build output

StudioBridge-src/.github/entitlements.plist

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+    <!-- Required for JVM JIT compilation under hardened runtime -->
+    <key>com.apple.security.cs.allow-jit</key>
+    <true/>
+    <!-- Required for JVM memory management under hardened runtime -->
+    <key>com.apple.security.cs.allow-unsigned-executable-memory</key>
+    <true/>
+</dict>
+</plist>