feat(cli): add Bun single executable binary support

Enables building hapi as standalone Bun-compiled executables for macOS,
Linux, and Windows (x64/arm64). Adds build script, bootstrap entry point,
runtime asset management, and automatic deployment of bundled tools
(ripgrep, difftastic). Includes MCP stdio bridge support and proper
environment handling for compiled binaries. Updates documentation with
build and installation instructions for single executable distribution.

cli/src/codex/runCodex.ts

@@ -16,6 +16,7 @@ import os from 'node:os';
 import { MessageQueue2 } from '@/utils/MessageQueue2';
 import { hashObject } from '@/utils/deterministicJson';
 import { runtimePath } from '@/projectPath';
+import { getHappyCliCommand } from '@/utils/spawnHappyCLI';
 import { resolve, join } from 'node:path';
 import fs from 'node:fs';
 import { startHappyServer } from '@/claude/utils/startHappyServer';
@@ -521,11 +522,11 @@ export async function runCodex(opts: {
 
     // Start Happy MCP server (HTTP) and prepare STDIO bridge config for Codex
     const happyServer = await startHappyServer(session);
-    const bridgeCommand = join(runtimePath(), 'bin', 'happy-mcp.mjs');
+    const bridgeCommand = getHappyCliCommand(['mcp', '--url', happyServer.url]);
     const mcpServers = {
         happy: {
-            command: bridgeCommand,
-            args: ['--url', happyServer.url]
+            command: bridgeCommand.command,
+            args: bridgeCommand.args
         }
     } as const;
     let first = true;