backend-infra-engineer: Post v0.3.9-hotfix7 snapshot (build cleanup)

docs/public/release-notes.md

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+# Release Notes
+
+## v0.5.0-alpha (In Development)
+
+**Type:** Major Feature & Architecture Update
+**Date:** TBD
+
+### 🎵 New Music Editor
+The highly anticipated SPC Music Editor is now available!
+- **Tracker View:** Edit music patterns with a familiar tracker interface.
+- **Piano Roll:** Visualize and edit notes with velocity and duration control.
+- **Preview:** Real-time N-SPC audio preview with authentic ADSR envelopes.
+- **Instruments:** Manage instruments and samples directly.
+
+### 🕸️ Web App Improvements (WASM)
+- **Experimental Web Port:** Run YAZE directly in your browser.
+- **UI Refresh:** New panelized layout with VSCode-style terminal and problems view.
+- **Usability:** Improved error handling for missing features (Emulator).
+- **Security:** Hardened `SharedArrayBuffer` support with `coi-serviceworker`.
+
+### 🏗️ Architecture & CI
+- **Windows CI:** Fixed environment setup for `clang-cl` builds (MSVC dev cmd).
+- **Code Quality:** Consolidated CI workflows.
+- **SDL3 Prep:** Groundwork for the upcoming migration to SDL3.
+
+---
+
+## v0.4.0 - Music Editor & UI Polish
+**Released:** November 2025
+
+- Complete SPC music editing infrastructure.
+- EditorManager refactoring for better multi-window support.
+- AI Agent integration (experimental).