chore: add project docs, glossary, research and opencode/fastcrw skills

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

CLAUDE.md

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+## Agent skills
+
+### Issue tracker
+
+Issues are tracked in Gitea (git.arthurerlich.de) via the `tea` CLI. See `docs/agents/issue-tracker.md`.
+
+### Triage labels
+
+Default vocabulary: `needs-triage`, `needs-info`, `ready-for-agent`, `ready-for-human`, `wontfix`. See `docs/agents/triage-labels.md`.
+
+### Domain docs
+
+Single-context: one `CONTEXT.md` + `docs/adr/` at the repo root. See `docs/agents/domain.md`.