fix: tab highlight reactivity, cleanup docs and build scripts

- Fix tab highlight not updating visually — switch from class={tabClass()}
  to Svelte's class:active directive for proper reactive class binding
- Rewrite README.md with full project structure, architecture, build guide
- Rewrite build.sh to build both GUI and server, output to build/
- Add scripts/build.sh for granular builds (gui/server/all)
- Add build/, frontend-dist/, and test vault dirs to .gitignore
- Remove stale binaries from project root
- Update AGENTS.md session summary

.gitignore

@@ -20,6 +20,7 @@ go.work
 
 # Wails
 frontend/dist/
+frontend/frontend-dist/
 frontend/node_modules/
 frontend/bindings/
 /verstak-gui
@@ -42,3 +43,8 @@ Thumbs.db
 # Vault test data
 test-vault/
 server-data/
+Ромашка/
+Тестовая папка/
+
+# Build output
+build/