Add symposium-rust-lang skill

skills/symposium-rust-lang/SKILL.md

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+---
+name: symposium-rust-lang
+description: "Use when asking about Rust code style or best practices. Keywords: naming, formatting, comment, clippy, rustfmt, lint, code style, best practice, P.NAM, G.FMT, code review, naming convention, variable naming, function naming, type naming.
+user-invocable: false
+---
+
+# Rust Coding Guidelines (50 Core Rules)
+
+## Naming (Rust-Specific)
+
+| Rule | Guideline |
+|------|-----------|
+| No `get_` prefix | `fn name()` not `fn get_name()` |
+| Iterator convention | `iter()` / `iter_mut()` / `into_iter()` |
+| Conversion naming | `as_` (cheap &), `to_` (expensive), `into_` (ownership) |
+| Static var prefix | `G_CONFIG` for `static`, no prefix for `const` |
+
+## Data Types
+
+| Rule | Guideline |
+|------|-----------|
+| Use newtypes | `struct Email(String)` for domain semantics |
+| Prefer slice patterns | `if let [first, .., last] = slice` |
+| Pre-allocate | `Vec::with_capacity()`, `String::with_capacity()` |
+| Avoid Vec abuse | Use arrays for fixed sizes |
+
+## Strings
+
+| Rule | Guideline |
+|------|-----------|
+| Prefer bytes | `s.bytes()` over `s.chars()` when ASCII |
+| Use `Cow<str>` | When might modify borrowed data |
+| Use `format!` | Over string concatenation with `+` |
+| Avoid nested iteration | `contains()` on string is O(n*m) |
+
+## Error Handling
+
+| Rule | Guideline |
+|------|-----------|
+| Use `?` propagation | Not `try!()` macro |
+| `expect()` over `unwrap()` | When value guaranteed |
+| Assertions for invariants | `assert!` at function entry |
+
+## Memory
+
+| Rule | Guideline |
+|------|-----------|
+| Meaningful lifetimes | `'src`, `'ctx` not just `'a` |
+| `try_borrow()` for RefCell | Avoid panic |
+| Shadowing for transformation | `let x = x.parse()?` |
+
+## Concurrency
+
+| Rule | Guideline |
+|------|-----------|
+| Identify lock ordering | Prevent deadlocks |
+| Atomics for primitives | Not Mutex for bool/usize |
+| Choose memory order carefully | Relaxed/Acquire/Release/SeqCst |
+
+## Async
+
+| Rule | Guideline |
+|------|-----------|
+| Sync for CPU-bound | Async is for I/O |
+| Don't hold locks across await | Use scoped guards |
+
+## Macros
+
+| Rule | Guideline |
+|------|-----------|
+| Avoid unless necessary | Prefer functions/generics |
+| Follow Rust syntax | Macro input should look like Rust |
+
+## Deprecated → Better
+
+| Deprecated | Better | Since |
+|------------|--------|-------|
+| `lazy_static!` | `std::sync::OnceLock` | 1.70 |
+| `once_cell::Lazy` | `std::sync::LazyLock` | 1.80 |
+| `std::sync::mpsc` | `crossbeam::channel` | - |
+| `std::sync::Mutex` | `parking_lot::Mutex` | - |
+| `failure`/`error-chain` | `thiserror`/`anyhow` | - |
+| `try!()` | `?` operator | 2018 |
+
+## Quick Reference
+
+```
+Naming: snake_case (fn/var), CamelCase (type), SCREAMING_CASE (const)
+Format: rustfmt (just use it)
+Docs: /// for public items, //! for module docs
+Lint: #![warn(clippy::all)]
+```
+
+Claude knows Rust conventions well. These are the non-obvious Rust-specific rules.