chore: import .claude command skills, CLAUDE.md, .gitignore, next_steps.md

- Vendor local .claude/ command skills (autopilot, plan, implement, etc.)
- Add CLAUDE.md pointing slash commands to .claude/commands/*/SKILL.md
- Untrack docs-Lokal/ and ignore .planning/ for local-only planning docs
- Include next_steps.md pulled from upstream

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

.claude/rules/rust.mdc

@@ -0,0 +1,17 @@
+---
+description: "Rust coding conventions: error handling with Result/thiserror/anyhow, ownership patterns, clippy, module structure"
+globs: ["**/*.rs", "**/Cargo.toml", "**/Cargo.lock"]
+---
+# Rust
+
+- Use `Result<T, E>` for recoverable errors; `panic!` only for unrecoverable
+- Use `?` operator for error propagation; define custom error types with `thiserror`; use `anyhow` for application-level errors
+- Prefer references over cloning; minimize unnecessary allocations
+- Never use `unwrap()` in production code; use `expect()` with descriptive message or proper error handling
+- Minimize `unsafe`; document invariants when used; isolate in separate modules
+- Use `Arc<Mutex<T>>` for shared mutable state; prefer channels (`mpsc`) for message passing
+- Use `clippy` and `rustfmt`; treat clippy warnings as errors in CI
+- Module structure: `src/main.rs` or `src/lib.rs` as entry; submodules in separate files
+- Use `#[cfg(test)]` module for unit tests; `tests/` directory for integration tests
+- Use feature flags for conditional compilation
+- Use `serde` for serialization with `derive` feature