docs(skills): refresh gardening milestone/label snapshot after 2026-07-25 backlog drain

[JSONbored]

Summary

• Wave 1-4 milestones (505 issues total), the ~120-issue "MCP execute" family, and the generated-types epic (Epic: generated types everywhere — Zod as the boundary source of truth, codegen for DB/GraphQL/MCP, docs from the generated contract #7858) all closed out between 2026-07-20 and 2026-07-25, dropping this repo's open-issue count from a historical ~94-142 to 28 — with zero contributor-available issues at the start of this gardening run.
• Refreshes .claude/skills/contributor-pipeline-gardening/reference.md's milestone taxonomy table and label-density stats, which were describing a five-hundred-issue backlog that no longer exists.
• Adds a "where contributor-available issues actually come from now" section documenting the two productive veins found this run (design-token lint-ratchet completion, generated-types epic follow-on batches) so future runs don't re-derive this from scratch.
• Updates SKILL.md's Pass-1 milestone/unmilestoned/native-staking notes to match.

Doc-only change against the gardening skill's own reference files — no code/schema changes.

Test plan

• npx prettier --check clean on both touched files

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.82%. Comparing base (1ada9a4) to head (93ef3e9).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8173   +/-   ##
=======================================
  Coverage   97.82%   97.82%           
=======================================
  Files         415      415           
  Lines       28893    28893           
  Branches    10850    10850           
=======================================
  Hits        28265    28265           
  Misses        141      141           
  Partials      487      487           

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