docs: add initial README and OpenSpec proposal

Add comprehensive README.md documenting project purpose, architecture,
tech stack, and development workflow. Includes OpenSpec proposal
(add-initial-readme) with project documentation specification.

The README describes current state only (early development phase) and
serves as entry point for developers and AI assistants.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

openspec/changes/add-initial-readme/tasks.md

@@ -0,0 +1,13 @@
+# Implementation Tasks
+
+## 1. Documentation
+- [x] 1.1 Draft README.md content reflecting current project state
+- [x] 1.2 Include project overview and purpose
+- [x] 1.3 Document OpenSpec workflow for contributors
+- [x] 1.4 Add getting started section for contributors
+- [x] 1.5 Include license and contact information
+- [x] 1.6 Review README.md for accuracy against project.md
+
+## 2. Validation
+- [x] 2.1 Verify OpenSpec validation passes
+- [x] 2.2 Ensure README.md aligns with openspec/project.md conventions