Add terminal screenshots or demo recording to README

[bobbyjohnstx]

Problem

No screenshots or demo recordings exist in README or anywhere in the repo. A comparison doc exists (tinycode-vs-open-webui.md) but no comparisons against primary competitors (Claude Code, aider, Cursor). No good-first-issue label convention visible.

Fix

• Add 1-2 terminal screenshots or an asciinema/GIF recording to README (standard for developer tools)
• Skip comparison docs for now — they go stale and create maintenance burden

Priority

MINOR — marketing/adoption concern, not a blocker

---

From: contributor readiness review (architect + critic validated)