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)

scripts/build-host.js

@@ -1,7 +1,14 @@
 #!/usr/bin/env node
 /**
- * Build script for the native host.
- * Generates the holesail-browser-host launcher script.
+ * Build script for the native host launcher.
+ *
+ * Generates `native-host/holesail-browser-host` — a bash script that invokes
+ * `bare native-host/index.mjs`. The `bare` binary is located by:
+ *   1. `which bare` (PATH lookup)
+ *   2. Common Homebrew paths (/opt/homebrew/bin/bare, /usr/local/bin/bare)
+ *   3. Sibling of the current `node` binary as a last resort
+ *
+ * Run via: npm run build:host
  */
 
 const fs = require('fs');

scripts/run-install.js

@@ -1,5 +1,12 @@
 #!/usr/bin/env node
 'use strict';
+/**
+ * Cross-platform installer launcher.
+ * Spawns `scripts/install.sh` on macOS/Linux or `scripts/install.ps1` on Windows
+ * (via PowerShell with -ExecutionPolicy Bypass). Inherits stdio and forwards the exit code.
+ *
+ * Run via: npm run setup
+ */
 var path = require('path');
 var spawn = require('child_process').spawn;
 var isWin = process.platform === 'win32';