feat(skills): add rust style skill

src/skills/rust-style/SKILL.md

@@ -0,0 +1,34 @@
+---
+name: rust-style
+description: Use when creating, editing, or reviewing Rust files in this repository.
+---
+
+# rust-style
+
+Use this skill as the source of truth for repository Rust conventions.
+
+## Load rules
+
+Read every Markdown file directly under [`rules/`](rules/) before applying this skill.
+Resolve [`rules/`](rules/) relative to this `SKILL.md`.
+
+Finish when all discovered rule files have been read.
+
+## Apply rules
+
+Apply the loaded rules when editing or reviewing Rust files.
+When loaded rules conflict, follow the most specific rule.
+
+After editing Rust files, run:
+
+```bash
+nix run .#fix
+```
+
+Finish when `nix run .#fix` succeeds and the Rust change follows the loaded rules.
+If the command fails, report the failure.
+
+## Maintain rules
+
+When adding or changing files under [`rules/`](rules/), read [`RULE-FORMAT.md`](RULE-FORMAT.md) first.
+Finish when the changed rule files follow that format.