docs: drop audit-skill-md skill

The skill as written pushed for every public method to be mentioned
in `SKILL.md`, which is the wrong goal. `SKILL.md` is a distilled
agent guide of idiomatic patterns and pitfalls, not an API reference
-- autoapi-generated docs and module docstrings already provide full
per-method coverage. An audit pressing for 100% method coverage would
bloat the skill file into a stale copy of that reference.

The two checks with actual value (stale mentions in `SKILL.md`, and
drift between `functions.__all__` and the categorized function list)
are small enough to be ad-hoc greps at release time and do not
warrant a dedicated skill.

Also remove references to the skill from `AGENTS.md` and the
`write-dataframe-code` skill's "Related" section.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: timsaucer

.ai/skills/audit-skill-md/SKILL.md

@@ -148,5 +148,3 @@ function exposes a non-obvious option, add a short usage example.
   (users and agents).
 - `.ai/skills/check-upstream/` — audit upstream Apache DataFusion features
   and flag what the Python bindings do not yet expose.
-- `.ai/skills/audit-skill-md/` — audit the repo-root `SKILL.md` against the
-  current public Python API and flag drift.

.ai/skills/write-dataframe-code/SKILL.md

@@ -42,9 +42,6 @@ Currently available skills:
   contributor-facing guide for writing idiomatic DataFrame code inside this
   repo (TPC-H pattern index, plan-comparison diagnostic, docstring
   conventions). Layers on top of the user-facing [`SKILL.md`](SKILL.md).
-- [`audit-skill-md`](.ai/skills/audit-skill-md/SKILL.md) — cross-reference
-  the repo-root `SKILL.md` against the current public Python API and report
-  new APIs needing coverage and stale mentions. Run after upstream syncs.
 
 ## Plan-comparison diagnostic