feat(node): add TypeScript sibling project for npm-based install

Introduces @kuns/claude-mailbox under node/, a wire-compatible TypeScript
port of the .NET daemon that distributes via the public Gitea npm registry.
The .NET project stays in src/ClaudeMailbox/ untouched; users pick whichever
flavor they prefer.

- node/ project: fastify + @modelcontextprotocol/sdk StreamableHTTPServerTransport
  + better-sqlite3, schema and wire surface match the C# version (port 47822,
  X-Mailbox header, MCP tool names, snake_case SQLite columns)
- Cross-platform autostart: Scheduled Task (Win, no admin) / Windows Service
  (Win, --service) / launchd (mac) / systemd --user (linux)
- 9/9 vitest tests pass; end-to-end /health + send/check round-trip verified
- CI split: existing ci.yml/release.yml renamed to *-dotnet.yml with path
  filters, new ci-node.yml and release-node.yml publish to Gitea npm registry
- install.ps1 / install.sh bootstrap one-liners at repo root; homebrew/
  contains a tap formula template
- README install section reordered: npm path primary, dotnet publish secondary

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

install.ps1

@@ -0,0 +1,46 @@
+#Requires -Version 5.1
+<#
+.SYNOPSIS
+  Bootstrap installer for ClaudeMailbox on Windows.
+
+.DESCRIPTION
+  Configures the @kuns scoped npm registry to point at the public Gitea
+  package registry, installs @kuns/claude-mailbox globally, and optionally
+  registers per-user autostart via Scheduled Task.
+
+.PARAMETER NoAutostart
+  Skip the install-autostart step.
+
+.PARAMETER Service
+  Install as a Windows Service (admin shell required) instead of a Scheduled Task.
+
+.EXAMPLE
+  irm https://git.kuns.dev/releases/ClaudeMailbox/raw/branch/main/install.ps1 | iex
+#>
+[CmdletBinding()]
+param(
+  [switch] $NoAutostart,
+  [switch] $Service
+)
+
+$ErrorActionPreference = "Stop"
+
+if (-not (Get-Command npm -ErrorAction SilentlyContinue)) {
+  throw "Node.js / npm not found on PATH. Install Node 20+ from https://nodejs.org and retry."
+}
+
+Write-Host "Configuring @kuns scoped npm registry..." -ForegroundColor Cyan
+npm config set "@kuns:registry" "https://git.kuns.dev/api/packages/releases/npm/"
+
+Write-Host "Installing @kuns/claude-mailbox globally..." -ForegroundColor Cyan
+npm install -g "@kuns/claude-mailbox"
+
+if (-not $NoAutostart) {
+  $args = @("install-autostart")
+  if ($Service) { $args += "--service" }
+  Write-Host "Registering autostart..." -ForegroundColor Cyan
+  & claude-mailbox @args
+}
+
+Write-Host ""
+Write-Host "ClaudeMailbox installed. Run 'claude-mailbox status' to verify." -ForegroundColor Green