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>

homebrew/claude-mailbox.rb

@@ -0,0 +1,29 @@
+# Homebrew formula for ClaudeMailbox.
+#
+# Publish this file to your tap repo (e.g. kuns/homebrew-tap as
+# Formula/claude-mailbox.rb), then on a Mac:
+#
+#   brew tap kuns/tap https://git.kuns.dev/kuns/homebrew-tap.git
+#   brew install kuns/tap/claude-mailbox
+#
+# The formula thin-wraps the @kuns/claude-mailbox npm package: it relies on
+# Homebrew's `node` formula and runs `npm install -g` into a private libexec,
+# then symlinks the bin into Homebrew's prefix so the binary lands on PATH.
+class ClaudeMailbox < Formula
+  desc "Standalone MCP mail server for parallel Claude session coordination"
+  homepage "https://git.kuns.dev/releases/ClaudeMailbox"
+  url "https://git.kuns.dev/api/packages/releases/npm/@kuns/claude-mailbox/-/@kuns/claude-mailbox-VERSION.tgz"
+  sha256 "REPLACE_WITH_SHA256_OF_THE_TARBALL"
+  license "MIT"
+
+  depends_on "node"
+
+  def install
+    system "npm", "install", *Language::Node.std_npm_install_args(libexec)
+    bin.install_symlink Dir["#{libexec}/bin/*"]
+  end
+
+  test do
+    assert_match "claude-mailbox", shell_output("#{bin}/claude-mailbox --version")
+  end
+end