Upstream assess

Vendor-pull process for absorbing changes from pingdotgg/t3code into gannonh/kata-code.

This is the active upstream strategy per ADR 0004 — Selective vendor-pull. It replaced the abandoned episodic bulk-merge approach (ADR 0003). The unit of work is a single upstream change ported as a fork-original commit, not a merged range.

The docs live in the OKF bundle:

• Policy: ADR 0004 and the superseded ADR 0003
• Runbook mirror: docs/guides/upstream-sync.md
• Divergence log + last scan baseline: FORK.md

What this skill does

Walks the human from "what has upstream done?" to a concrete, per-change decision about what to bring in. Five phases: