refactor: simplify compile.ts to single-target and add per-platform compile scripts

- Rewrite compile.ts from 112 to 66 lines: single target with auto-detect host, remove multi-target batch logic
- Add compile:linux/mac/win scripts to server, root, and turbo configs
- Wire desktop dist:* to depend on matching server compile:* (avoid unnecessary cross-platform compilation)
- Update AGENTS.md docs across root, server, and desktop

AGENTS.md

@@ -20,7 +20,10 @@ Guidelines for AI agents working in this Bun monorepo.
 ```bash
 bun dev            # Start all apps in dev mode
 bun build          # Build all apps
-bun compile        # Compile server to standalone binary (depends on build)
+bun compile        # Compile server to standalone binary (current platform, depends on build)
+bun compile:linux  # Compile server for Linux x64
+bun compile:mac    # Compile server for macOS arm64
+bun compile:win    # Compile server for Windows x64
 bun dist           # Full packaging pipeline: server build → compile → desktop distributable (current platform)
 bun dist:linux     # Full pipeline → Linux distributable
 bun dist:mac       # Full pipeline → macOS distributable
@@ -33,7 +36,10 @@ bun typecheck      # TypeScript check across monorepo
 ```bash
 bun dev                   # Vite dev server (localhost:3000)
 bun build                 # Production build -> .output/
-bun compile               # Compile to standalone binary
+bun compile               # Compile to standalone binary (current platform)
+bun compile:linux         # Compile for Linux x64
+bun compile:mac           # Compile for macOS arm64
+bun compile:win           # Compile for Windows x64
 bun fix                   # Biome auto-fix
 bun typecheck             # TypeScript check