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>

node/src/config.ts

@@ -0,0 +1,91 @@
+import { existsSync, readFileSync } from "node:fs";
+import { homedir } from "node:os";
+import { join, resolve } from "node:path";
+
+export const DEFAULT_PORT = 47822;
+export const DEFAULT_BIND = "127.0.0.1";
+
+export interface FileConfig {
+  port?: number;
+  bind?: string;
+  dbPath?: string;
+}
+
+export interface DaemonConfig {
+  port: number;
+  bind: string;
+  dbPath: string;
+}
+
+export function defaultDbPath(): string {
+  return join(homedir(), ".claude-mailbox", "mailbox.db");
+}
+
+export function userConfigPath(): string {
+  return join(homedir(), ".claude-mailbox", "mailbox.json");
+}
+
+export function machineConfigPath(): string | null {
+  if (process.platform === "win32") {
+    const programData = process.env["ProgramData"] ?? "C:\\ProgramData";
+    return join(programData, "ClaudeMailbox", "mailbox.json");
+  }
+  if (process.platform === "darwin") {
+    return "/Library/Application Support/ClaudeMailbox/mailbox.json";
+  }
+  return "/etc/claude-mailbox/mailbox.json";
+}
+
+function expandPath(p: string): string {
+  let out = p;
+  if (out.startsWith("~")) out = join(homedir(), out.slice(1));
+  out = out.replace(/%([^%]+)%/g, (_, name) => process.env[name] ?? "");
+  out = out.replace(/\$([A-Za-z_][A-Za-z0-9_]*)/g, (_, name) => process.env[name] ?? "");
+  return resolve(out);
+}
+
+export function loadFileConfig(explicitPath?: string): FileConfig {
+  const candidates: string[] = [];
+  if (explicitPath) {
+    if (!existsSync(explicitPath)) {
+      throw new Error(`Config file not found: ${explicitPath}`);
+    }
+    candidates.push(explicitPath);
+  } else {
+    candidates.push(userConfigPath());
+    const machine = machineConfigPath();
+    if (machine) candidates.push(machine);
+  }
+
+  for (const path of candidates) {
+    if (existsSync(path)) {
+      const raw = readFileSync(path, "utf8");
+      const parsed = JSON.parse(raw) as FileConfig;
+      return {
+        port: typeof parsed.port === "number" ? parsed.port : undefined,
+        bind: typeof parsed.bind === "string" ? parsed.bind : undefined,
+        dbPath: typeof parsed.dbPath === "string" ? parsed.dbPath : undefined,
+      };
+    }
+  }
+  return {};
+}
+
+export interface ServeOverrides {
+  port?: number;
+  bind?: string;
+  dbPath?: string;
+  config?: string;
+}
+
+export function resolveConfig(overrides: ServeOverrides): DaemonConfig {
+  const file = loadFileConfig(overrides.config);
+  const port = overrides.port ?? file.port ?? DEFAULT_PORT;
+  const bind = overrides.bind ?? file.bind ?? DEFAULT_BIND;
+  const dbPathRaw = overrides.dbPath ?? file.dbPath ?? defaultDbPath();
+  return { port, bind, dbPath: expandPath(dbPathRaw) };
+}
+
+export function baseUrl(cfg: { port: number; bind: string }): string {
+  return `http://${cfg.bind}:${cfg.port}`;
+}