v0.5.0: Experimental positioning and documentation overhaul

What changed

SubLLM's public documentation and package metadata now reflect its actual scope: an experimental, personal-use gateway — not a product pitch or commercial proxy.

Documentation

• Reframe project positioning — tagline, motivation, feature bullets, usage guidance, and terms section rewritten from assertive product pitch to conservative experimental framing
• Remove internal planning docs — docs/DESIGN.md (architecture, roadmap) and docs/RESEARCH.md (latency analysis, feature parity) deleted; content remains in git history
• Add experimental scope disclaimer — first bullet in the supported contract section marks the package as experimental and personal-use, applied in both README and code-generated docs source (docs.py)
• Align benchmark table formatting — consistent column alignment across Auth Check, Completion, Multi-turn, and Cross-provider Handoff tables

Package metadata

• Description updated to match experimental positioning across pyproject.toml, __init__.py module docstring, and README tagline
• Keywords changed from proxy, subscription to cli, gateway
• Telemetry resource version updated from hardcoded 0.4.0 to 0.5.0

What this release is NOT

No functional changes to providers, router, types, server, CLI, or test suite. All behavioral code is identical to v0.4.0. This release is purely documentation, metadata, and positioning.

Full diff: v0.4.0...v0.5.0