Add README with build and test instructions

README.md

@@ -0,0 +1,69 @@
+# MonoStep
+
+A monophonic 2-oscillator step-sequencer synthesizer implemented as a VST3 plugin with JUCE.
+
+## Features
+
+- 16-step monophonic sequencer (pattern length 1-16)
+- 2 oscillators with sine / triangle / saw / square waves, detune, and mix
+- Subtractive filter (cutoff, resonance) with ADSR and glide
+- Per-step gates, pitches (+/- 6 semitones), fine tuning (cents), and slide (legato)
+- Matrix editor with click-to-toggle steps, drag-to-pitch, and a slide row
+- Rotary-knob GUI with zoom (100% - 200%), a step panel with fine-tune, and a
+  live red play-position marker
+- Footer status bar showing the git commit and build date
+- Pattern stored in the plugin state (save/restore with the DAW)
+
+## Requirements
+
+- macOS 12.0 or later (arm64)
+- CMake 3.22 or newer
+- A C++17 compiler (Xcode command-line tools)
+- [JUCE](https://github.com/juce-framework/JUCE)
+
+## Building
+
+The build expects JUCE in `../juce` relative to this repository. If JUCE lives
+somewhere else, point `JUCE_DIR` at it during configuration.
+
+```sh
+# 1. Get JUCE next to this repository:
+git clone --depth 1 https://github.com/juce-framework/JUCE.git ../juce
+
+# 2. Configure:
+cmake -S . -B build
+
+# or, for a custom JUCE location:
+cmake -S . -B build -DJUCE_DIR=/path/to/juce
+
+# 3. Build the plugin:
+cmake --build build --target MonoStep_VST3
+```
+
+The VST3 plugin is written to:
+
+```
+build/MonoStep_artefacts/Release/VST3/MonoStep.vst3
+```
+
+### Installing
+
+Copy the bundle into your DAW's VST3 directory:
+
+```sh
+cp -R build/MonoStep_artefacts/Release/VST3/MonoStep.vst3 \
+      ~/Library/Audio/Plug-Ins/VST3/
+```
+
+## Running the tests
+
+Build the headless host test and run it against the built plugin:
+
+```sh
+cmake --build build --target MonoStepTestHost
+build/MonoStepTestHost_artefacts/Release/MonoStepTestHost \
+    build/MonoStep_artefacts/Release/VST3/MonoStep.vst3
+```
+
+The host scans the VST3, renders a buffer, and verifies that the pattern
+survives a state save/load round-trip. Expect `ALL TESTS PASSED`.