chore(docs): README — add a work-in-progress warning (in the product's own voice) #493

Important

Problem

The README pitches the studio confidently but never says it's pre-release — a first-time visitor has no signal that edges are rough and reports are wanted.

Approach

A single GitHub > [!WARNING] callout directly under the hero block, written in Amicode's own vocabulary so the warning doubles as a product thesis: superposition (research tool vs construction site), the F ≥ 0.99 promotion discipline applied to the product itself, and Amicode: Report a Bug as the warm-start loop for feedback.

Scope

In: README.md, one callout. Out: extension README (already carries "Pre-release software" in its subtitle); any capability copy changes.