feat(build): add parallel builds and consolidate build system

Enhance build.mjs with comprehensive multi-target and platform build support, eliminating the need for separate build-platforms.mjs wrapper script.

New features:
- Build multiple targets: --targets cli,sea,darwin-arm64
- Build all platforms: --platforms (8 platform targets)
- Parallel builds: --parallel (for faster multi-target builds)
- Sequential builds: default for --targets and --platforms

Platform targets supported:
- alpine-arm64, alpine-x64
- darwin-arm64, darwin-x64
- linux-arm64, linux-x64
- win32-arm64, win32-x64

Examples:
- pnpm run build --platforms                    # All platforms sequentially
- pnpm run build --platforms --parallel         # All platforms in parallel
- pnpm run build --targets cli,sea --parallel   # Multiple targets in parallel

Update README.md with progressive build documentation from easiest to most advanced:
1. Quick start (default smart build)
2. Force rebuild
3. Single target builds
4. Multiple target builds
5. Platform binaries
6. Advanced direct package builds

Remove:
- build:platforms npm script (replaced by --platforms flag)
- scripts/build-platforms.mjs (functionality integrated into build.mjs)

Author: jdalton

README.md

@@ -119,12 +119,12 @@ Socket CLI uses an **intelligent build system with automatic caching** that only
 3. **CLI Package** - TypeScript compilation and bundling
 4. **SEA Binary** - Node.js Single Executable Application
 
-#### Smart build (recommended)
+#### Quick start (easiest)
 
 The default build command automatically skips packages that are already up-to-date:
 
 ```bash
-# Build only what changed (simulates CI caching locally)
+# Build only what changed (recommended for development)
 pnpm run build
 ```
 
@@ -160,34 +160,57 @@ Total:    57.4s
 
 #### Force rebuild
 
-To force rebuild all packages (ignoring cache):
+To rebuild everything from scratch (ignoring cache):
 
 ```bash
-# Rebuild everything from scratch
+# Force rebuild all packages
 pnpm run build --force
 ```
 
-#### Build specific packages
+#### Single target builds
 
-For targeted builds during development:
+For fast iteration during development:
 
 ```bash
-# Build only CLI package (fast iteration)
+# Build only CLI package
 pnpm run build --target cli
 
 # Build SEA binary
 pnpm run build --target sea
 
 # Build specific platform binary
 pnpm run build --target darwin-arm64
+```
 
-# See all available targets
-pnpm run build --help
+#### Multiple target builds
+
+Build multiple packages at once:
+
+```bash
+# Build multiple specific targets sequentially
+pnpm run build --targets cli,sea,darwin-arm64
+
+# Build multiple targets in parallel (faster)
+pnpm run build --targets cli,sea,darwin-arm64 --parallel
+```
+
+#### Platform binaries
+
+Build all platform binaries (8 platforms):
+
+```bash
+# Build all platforms sequentially (safer for limited resources)
+pnpm run build --platforms
+
+# Build all platforms in parallel (much faster, requires more CPU/RAM)
+pnpm run build --platforms --parallel
 ```
 
-#### Manual builds
+**Platform targets:** alpine-arm64, alpine-x64, darwin-arm64, darwin-x64, linux-arm64, linux-x64, win32-arm64, win32-x64
 
-You can also build individual packages directly:
+#### Advanced: Direct package builds
+
+Build individual packages directly with pnpm filters:
 
 ```bash
 # Build ONNX Runtime WASM (for AI features)
@@ -203,6 +226,12 @@ pnpm --filter @socketsecurity/cli run build
 pnpm --filter @socketbin/node-sea-builder-builder run build
 ```
 
+#### All build options
+
+```bash
+pnpm run build --help
+```
+
 See [docs/development/](docs/development/) for detailed development guides.
 
 ### Development environment variables

package.json

@@ -169,7 +169,6 @@
     "// Build": "",
     "build": "node scripts/build.mjs",
     "build:cli": "pnpm --filter @socketsecurity/cli run build",
-    "build:platforms": "node scripts/build-platforms.mjs",
     "build:watch": "pnpm --filter @socketsecurity/cli run build:watch",
     "dev": "pnpm run build:watch",
     "// Quality Checks": "",