rewrite readme to focus on motivations; move features into docs/

[cjus]

Summary

• Rewrite README around three questions: what is this, why is it different, why might it be useful. Reduced from 234 → 61 lines.
• Tagline updated from technical "agent loop" framing to "personal Agent"; positioning leads with local-Ollama economics + paid Claude escalation.
• "Why Solrac" section explicitly contrasts against OpenClaw and Hermes Agent so readers can self-select.
• FEATURES.md moved to docs/FEATURES.md; relative links inside the file updated (../README.md, ./USAGE.md#…).
• Documentation table at the bottom of the README is now the canonical jump-off point into the docs/ tree.

Why

• Long READMEs are off-putting. The previous README mixed motivation, feature list, install instructions, repo layout, stack, design philosophy teaser, anti-goals teaser, testing block, and a multi-doc web-UI cross-reference list — much of which already lives canonically in docs/.
• Adjacent projects in this space (OpenClaw, Hermes Agent) lead with motivation and link out. Solrac should too.
• Naming the comparison projects directly is honest positioning — they're broader and better-resourced; Solrac's distinct value (local-first economics, cost enforcement, audit-before-acting, single-process minimalism) is what justifies its existence.

What's removed from the README (canonical content lives in docs)

• Repository layout tree → docs/ARCHITECTURE.md (module map)
• Stack list → docs/ARCHITECTURE.md
• Design philosophy teaser → docs/ARCHITECTURE.md#philosophy
• "What's intentionally not here" teaser → docs/ARCHITECTURE.md#anti-goals
• Testing commands → discoverable via `package.json`; covered in `docs/OPERATIONS.md`
• Engine routing table → `docs/USAGE.md#engine-routing-prefix-table`
• Operational dependencies bullets → `docs/SETUP.md`
• Web UI multi-doc cross-reference list → users navigate via the Documentation table

No anti-goals are being reversed.

Test plan

• Render the README on github.com/cjus/solrac to confirm link resolution and table formatting
• Verify `docs/FEATURES.md` renders with working `../README.md` and `./USAGE.md#…` anchors
• Confirm Documentation table links all resolve from the README's location