Add build infrastructure and QUICKSTART guide

- Build script (scripts/build.mjs) using esbuild with iterative stub creation
- Stubs for Bun compile-time intrinsics (feature(), MACRO, bun:bundle)
- Stub modules for feature-gated internal code paths
- QUICKSTART.md with 3 build options (pre-built, esbuild, Bun)
- tsconfig.json, package.json for build tooling

Build reaches ~95% — 108 remaining feature-gated modules need Bun runtime
for full dead code elimination. See QUICKSTART.md for details.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

QUICKSTART.md

@@ -0,0 +1,121 @@
+# Quick Start — Building from Source
+
+> **TL;DR**: A full rebuild requires **Bun** (not Node.js) for its compile-time
+> intrinsics (`feature()`, `MACRO`, `bun:bundle`). A best-effort build with
+> esbuild gets ~95% there but needs manual fixes for ~108 feature-gated modules.
+
+## Option A: Run the pre-built CLI (Recommended)
+
+The npm package already contains a compiled `cli.js`:
+
+```bash
+cd /path/to/parent/            # where package.json and cli.js live
+node cli.js --version           # → 2.1.88 (Claude Code)
+node cli.js -p "Hello Claude"   # Non-interactive mode
+
+# Or install globally:
+npm install -g .
+claude --version
+```
+
+**Authentication required**: Set `ANTROPIC_API_KEY` or run `node cli.js login`.
+
+## Option B: Build from Source (Best Effort)
+
+### Prerequisites
+
+```bash
+node --version   # >= 18
+npm --version    # >= 9
+```
+
+### Steps
+
+```bash
+cd claude-code-2.1.88/
+
+# 1. Install build dependency
+npm install --save-dev esbuild
+
+# 2. Run the build script
+node scripts/build.mjs
+
+# 3. If successful, run the output:
+node dist/cli.js --version
+```
+
+### What the Build Script Does
+
+| Phase | Action |
+|-------|--------|
+| **1. Copy** | `src/` → `build-src/` (original untouched) |
+| **2. Transform** | `feature('X')` → `false` (enables dead code elimination) |
+| **2b. Transform** | `MACRO.VERSION` → `'2.1.88'` (compile-time version injection) |
+| **2c. Transform** | `import from 'bun:bundle'` → stub import |
+| **3. Entry** | Create wrapper that injects MACRO globals |
+| **4. Bundle** | esbuild with iterative stub creation for missing modules |
+
+### Known Issues
+
+The source code uses **Bun compile-time intrinsics** that cannot be fully replicated with esbuild:
+
+1. **`feature('FLAG')` from `bun:bundle`** — Bun resolves this at compile time to `true`/`false` and eliminates dead branches. Our transform replaces with `false`, but esbuild still resolves `require()` inside those branches.
+
+2. **`MACRO.X`** — Bun's `--define` replaces these at compile time. We use string replacement, which works for most cases but can miss edge cases in complex expressions.
+
+3. **108 missing modules** — These are feature-gated internal modules (daemon, bridge assistant, context collapse, etc.) that don't exist in the published source. They're normally dead-code-eliminated by Bun but esbuild can't eliminate them because the `require()` calls are still syntactically present.
+
+4. **`bun:ffi`** — Used for native proxy support. Stubbed out.
+
+5. **TypeScript `import type` from generated files** — Some generated type files are not in the published source.
+
+### To Fix Remaining Issues
+
+```bash
+# 1. Check what's still missing:
+npx esbuild build-src/entry.ts --bundle --platform=node \
+  --packages=external --external:'bun:*' \
+  --log-level=error --log-limit=0 --outfile=/dev/null 2>&1 | \
+  grep "Could not resolve" | sort -u
+
+# 2. Create stubs for each missing module in build-src/src/:
+#    For JS/TS: create file exporting empty functions
+#    For text: create empty file
+
+# 3. Re-run:
+node scripts/build.mjs
+```
+
+## Option C: Build with Bun (Full Rebuild — Requires Internal Access)
+
+```bash
+# Install Bun
+curl -fsSL https://bun.sh/install | bash
+
+# The real build uses Bun's bundler with compile-time feature flags:
+# bun build src/entrypoints/cli.tsx \
+#   --define:feature='(flag) => flag === "SOME_FLAG"' \
+#   --define:MACRO.VERSION='"2.1.88"' \
+#   --target=bun \
+#   --outfile=dist/cli.js
+
+# However, the internal build configuration is not included in the
+# published package. You'd need access to Anthropic's internal repo.
+```
+
+## Project Structure
+
+```
+claude-code-2.1.88/
+├── src/                  # Original TypeScript source (1,884 files, 512K LOC)
+├── stubs/                # Build stubs for Bun compile-time intrinsics
+│   ├── bun-bundle.ts     #   feature() stub → always returns false
+│   ├── macros.ts         #   MACRO version constants
+│   └── global.d.ts       #   Global type declarations
+├── scripts/
+│   └── build.mjs         # Build script (esbuild-based)
+├── node_modules/         # 192 npm dependencies
+├── vendor/               # Native module source stubs
+├── build-src/            # Created by build script (transformed copy)
+└── dist/                 # Build output (created by build script)
+```