Add style-sweep skill: mechanical repo sweeps run as scripts, not agent fan-outs

.claude/skills/style-sweep/SKILL.md

@@ -0,0 +1,33 @@
+---
+name: style-sweep
+description: Run a mechanical, repo-wide text cleanup (character replacement,
+  whitespace/style normalization) as a deterministic script instead of agent
+  fan-out. Use whenever the ask is "remove/replace X across the repo" and the
+  transformation needs no judgment. Verifies with git diff + a small-model
+  spot check, never one agent per file.
+---
+
+# Style sweep
+
+Mechanical text transformations are script work. NEVER fan out agents to edit
+files one by one for a deterministic replacement: a script is faster, free,
+and reviewable as a single diff.
+
+1. **Express the transformation as a script.** Example (em dash to " - "):
+
+   ```bash
+   git ls-files '*.js' '*.ts' | xargs perl -CSD -pi -e 's/\x{2014}/ - /g'
+   ```
+
+   Scope with `git ls-files <globs>` so only tracked files change. For
+   context-dependent rules (e.g. only inside comments), write the script with
+   a proper parser (`ast-grep`, `codemod`): still a script, still one diff.
+
+2. **Verify deterministically first**: `git diff --stat`, then re-grep for the
+   target pattern (`git grep -P '\x{2014}' -- '*.js'` should return nothing).
+
+3. **Spot-check with ONE small-model subagent** (not one per file): give a
+   Haiku/Sonnet agent 10 random hunks from `git diff` and ask whether any
+   replacement changed meaning (string literals, URLs, test fixtures).
+
+4. Commit as a single sweep commit so review is one pass.