docs: rebrand messaging — 'the self-improving AI agent'

- Lead with the learning loop: autonomous skill creation, skill
  self-improvement, memory nudges, FTS5 session search, Honcho
  dialectic user modeling
- 'Runs anywhere' angle: 6 backends, serverless persistence with
  Daytona/Modal, not tied to your laptop
- 'Built by model trainers' replaces 'model-agnostic'
- Updated README tagline, feature table, subtitle
- Updated docs landing page hero, description, key features
- Updated docusaurus tagline and pyproject.toml description

pyproject.toml

@@ -5,7 +5,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "hermes-agent"
 version = "0.1.0"
-description = "AI agent with advanced tool-calling and toolsets"
+description = "The self-improving AI agent — creates skills from experience, improves them during use, and runs anywhere"
 readme = "README.md"
 requires-python = ">=3.11"
 authors = [{ name = "Nous Research" }]