Track upstream ductor release v0.20.1

[github-actions]

Upstream published a new release: v0.20.1.

• Published: 2026-07-23T07:45:09Z
• URL: https://github.com/PleasePrompto/ductor/releases/tag/v0.20.1

Suggested follow-up

1. Review the upstream changelog and commits.
2. Decide which changes need to be ported into this fork.
3. Track any fork-specific conflicts before merging or cherry-picking.

Upstream release notes

A housekeeping release: the onboarding wizard now detects Grok, Slack onboarding is fully translated and documented, and a repo-wide audit removed ~1,700 lines of dead code with zero behavior change.

TL;DR

• Wizard detects Grok — the onboarding CLI check now probes grok like the runtime already did, in all 8 languages.
• Slack polish — wizard sections translated in all 8 languages, ductor install slack added, plus a standalone Slack setup guide covering app creation, scopes, Socket Mode, and troubleshooting.
• Gemini access note — documented that Gemini CLI stopped serving free/Pro/Ultra individual accounts on 2026-06-18; API key and Code Assist licenses are unaffected, and Antigravity (agy) is the free path.
• ~1,700 lines removed — repo-wide over-engineering audit: verified dead code, test-only APIs, and duplicated helpers are gone; the four model-cache observers now share one generic base; docs updated to note AGENTS.md serves both Codex and Grok. No behavior change — 4,008 tests, strict mypy, and ruff all green.