docs: add CONTRIBUTING.md, CHANGELOG.md, and JSDoc to entire codebase

Add docs/CONTRIBUTING.md covering the build system, dev workflow, all
npm scripts, how to add new native host message types, code style, and
debugging guidance.

Add CHANGELOG.md at the project root documenting all features and fixes
across the 1.0.0 release.

Add JSDoc (@param, @returns) to all previously undocumented exported
functions across 35 JS files:
- native-host/holesail-manager/ (index, virtual-hosts, service-tunnels,
  servers, port-allocator)
- native-host top-level managers (startup, connect-proxy, https-proxy,
  certificate-authority, ssh-manager, rdp-manager)
- extension/background/ (logs, native-messaging, proxy, message-router)
- extension/dashboard/core/ (utils, navigation, init)
- extension/dashboard/ui/ (modal, toast, state-tag)
- extension/dashboard/pages/ (all 10 page files)
- extension/dashboard/refresh.js, events.js
- extension/dashboard/data/hostname-validator.js
- scripts/ (build-host, run-install)

extension/dashboard/pages/servers.js

@@ -1,5 +1,9 @@
-// Depends on: core/utils.js ($, escapeHtml, truncate), ui/toast.js (showToast, copyToClipboard),
-//             ui/modal.js (openModal, closeModal, showModalError)
+/**
+ * Server Tunnels page — renders the server table, manages bulk selection,
+ * and wires up start/stop/edit modal events.
+ * Depends on: core/utils.js ($, escapeHtml, truncate), ui/toast.js (showToast, copyToClipboard),
+ *             ui/modal.js (openModal, closeModal, showModalError)
+ */
 
 function _updateServerBulkBar() {
   const checked = document.querySelectorAll('#swarmsTable input[type="checkbox"]:checked');
@@ -14,6 +18,10 @@ function _updateServerBulkBar() {
   }
 }
 
+/**
+ * Re-render the server tunnels table with the latest state.
+ * @param {object} state - Full extension state from `fetchState()`.
+ */
 function updateSwarmsTable(state) {
   const tbody = $('swarmsTable');
   if (!tbody) return;
@@ -118,6 +126,10 @@ function updateSwarmsTable(state) {
   _updateServerBulkBar();
 }
 
+/**
+ * Attach all event listeners for the Server Tunnels page.
+ * Called once during dashboard initialisation.
+ */
 function setupServerEvents() {
   $('serverSelectAll')?.addEventListener('change', (e) => {
     document.querySelectorAll('#swarmsTable .server-row-cb').forEach(cb => { cb.checked = e.target.checked; });