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/package.json

@@ -62,6 +62,8 @@
     "why do we need to build before running tests / dev?": "We need the binary to be built so we run daemon commands which directly run the binary - we don't want them to go out of sync or have custom spawn logic depending how we started happy",
     "typecheck": "tsc --noEmit",
     "build": "shx rm -rf dist && tsc --noEmit && pkgroll",
+    "build:exe": "bun run scripts/build-executable.ts",
+    "build:exe:all": "bun run scripts/build-executable.ts --all",
     "test": "bun run build && tsx --env-file .env.integration-test node_modules/.bin/vitest run",
     "test:win": "bun run build && vitest run",
     "start": "bun run build && ./bin/happy.mjs",
@@ -87,9 +89,9 @@
     "ink": "^6.5.1",
     "ps-list": "^8.1.1",
     "react": "^19.2.0",
+    "react-devtools-core": "^7.0.1",
     "socket.io-client": "^4.8.1",
     "tar": "^7.5.2",
-    "tmp": "^0.2.5",
     "zod": "^3.23.8"
   },
   "devDependencies": {