feat: add build system, stubs, and npm packaging — openclaude is now runnable

- package.json with all 70+ dependencies
- Bun build script with feature flag shims, native module stubs, otel externals
- Stubs for ~15 missing source files (snapshot gaps)
- tsconfig.json for TypeScript
- bin/openclaude entry point
- Builds to single 19MB dist/cli.mjs
- Verified: --version and --help work

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

src/ink/devtools.ts

@@ -0,0 +1,2 @@
+// Stub — devtools not included in source snapshot
+export default {}

src/ink/global.d.ts

@@ -0,0 +1,9 @@
+// Stub — global types for Ink renderer
+declare namespace JSX {
+  interface IntrinsicElements {
+    'ink-box': Record<string, unknown>
+    'ink-text': Record<string, unknown>
+    'ink-root': Record<string, unknown>
+    'ink-virtual-text': Record<string, unknown>
+  }
+}