docs: add README, architecture, glossary, requirements; update CLAUDE.md

Add four Russian-language project documents:
- README.md: user-facing guide (install, quick start, data prep, training,
  evaluation, limitations)
- docs/architecture.md v1.0: system architecture, data flow diagrams,
  module interfaces, 7 architectural decision records, extension points
- docs/glossary.md v1.0: musical, ML, and project-specific term definitions
- docs/requirements.md v1.0: functional/non-functional requirements,
  acceptance criteria, four use-case scenarios

Update CLAUDE.md with project name etymology (hamori / ハモリ) and rename
repo root reference from chord-gen to hamori. Refine chord_format_spec.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/chord_format_spec.md

@@ -1,6 +1,4 @@
-# Спецификация формата данных
-
-## Проект: генератор аккордовых последовательностей
+# Спецификация формата данных hamori
 
 **Версия:** 2.0
 **Дата:** 2026-05-16