# Add `env:mod` with version + git hash

## Task
Add a PlatformIO environment that flashes firmware with a `-mod+<git_hash>` version suffix (e.g. `1.0.0-mod+a3f7c21`).

## Changes

### New file: `scripts/inject_mod_version.py`
- PlatformIO pre-build script
- Reads `version` from the `[crosspoint]` section of `platformio.ini`
- Runs `git rev-parse --short HEAD` to get the current commit hash
- Injects `-DCROSSPOINT_VERSION="{version}-mod+{hash}"` into build flags

### Modified: `platformio.ini`
- Added `[env:mod]` section (lines 58-64) that extends `base`, includes the new script via `extra_scripts`, and inherits base build flags

## Usage
```
pio run -e mod -t upload
```

## Follow-up
- None