🚧 Add build script

README.md

@@ -116,10 +116,52 @@ pip install -e .[dev]
 pytest
 ```
 
+## Building a self-executing exe
+
+The CLI can be packaged as a standalone Windows executable with PyInstaller.
+
+```bash
+pip install -e .[dev]      # includes pyinstaller
+
+# one-folder build (default): fast start-up, distribute the whole folder
+.\build.ps1
+
+# single-file build: one .exe, slower start-up (self-extracting)
+.\build.ps1 -Onefile
+
+# rebuild from scratch and smoke-test the exe against assets/
+.\build.ps1 -Clean -Test
+
+# explicit interpreter if several Pythons are installed
+.\build.ps1 -Python C:\Path\To\python.exe
+```
+
+Results land in `dist/`:
+
+- **one-folder** (default): `dist/mitsubishi-label-converter/mitsubishi-label-converter.exe`
+  plus supporting DLLs — distribute the whole folder; starts fast.
+- **onefile**: `dist/mitsubishi-label-converter.exe` — a single 8.8 MB file to
+  copy anywhere; a little slower to start.
+
+Notes:
+
+- The script prefers the project `.venv`, then `python`/`py` on PATH; the
+  Microsoft Store `python` alias is detected and skipped automatically.
+- `run.py` at the project root is the packaging entry point (PyInstaller cannot
+  execute `cli.py` directly because of its relative imports).
+- Antivirus software may flag unsigned PyInstaller exes; sign the exe or add
+  an exclusion if this matters in your environment.
+- Build artifacts (`build/`, `dist/`, `*.spec`) are git-ignored.
+
 ## TODO / Roadmap
 
 Done:
 
+- [x] **Self-executing exe** — `build.ps1` wraps PyInstaller with
+  one-folder/onefile modes, clean rebuild, built-in smoke test, and robust
+  Python resolution; verified all three subcommands and the lossless
+  round-trip through the packaged exe.
+
 - [x] **Expose struct members with addresses in Excel** — dotted member rows
   inline under each structured variable (189 structured variables -> 1,220
   member rows in the sample file).