chore: developer experience - pre-commit hook, ai instructions, yaml formatting (#374)

* chore: developer experience - pre-commit hook, ai instructions, yaml formatting for prettier

* no prettierrc, editorconfig instead

* fixes from copilot suggestions

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Co-authored-by: Ferdinand Schober <ferdinandschober20@gmail.com>

AGENTS.md

@@ -0,0 +1,65 @@
+# Lan Mouse Agent Instructions
+
+## Overview
+
+Lan Mouse is an open-source Software KVM sharing mouse/keyboard input across local networks. The Rust workspace combines a GTK frontend, CLI/daemon mode, and multi-OS capture/emulation backends for Linux, Windows, and macOS.
+
+## Core principles
+
+- **Scope discipline.** Only implement what was requested; describe follow-up work instead of absorbing it.
+- **Clarify OS behavior.** Ask when requirements touch OS-specific capture/emulation (they differ significantly).
+- **Docs stay current.** Update [README.md](README.md) or [DOC.md](DOC.md) when touching public APIs or platform support.
+- **Rust idioms.** Use `Result`/`Option`, `thiserror` for errors, descriptive logs, and concise comments for non-obvious invariants.
+
+## Terminology
+
+- **Client:** A remote machine that can receive or send input events. Each client is either _active_ (receiving events) or _inactive_ (can send events back). This mutual exclusion prevents feedback loops.
+- **Backend:** OS-specific implementation for capture or emulation (e.g., libei, layer-shell, wlroots, X11, Windows, macOS).
+- **Handle:** A per-client identifier used to route events and track state (pressed keys, position).
+
+## Architecture
+
+**Pipeline:** `input-capture` → `lan-mouse-ipc` → `input-emulation`
+
+- **input-capture:** Reads OS events into a `Stream<CaptureEvent>`. Backends tried in priority order (libei → layer-shell → X11 → fallback). Tracks `pressed_keys` to avoid stuck modifiers. `position_map` queues events when multiple clients share a screen edge.
+- **input-emulation:** Replays events via the `Emulation` trait (`consume`, `create`, `destroy`, `terminate`). Maintains `pressed_keys` and releases them on disconnect.
+- **lan-mouse-ipc / lan-mouse-proto:** Protocol glue and serialization. Events are UDP; connection requests are TCP on the same port. Version bumps required when serialization changes.
+- **input-event:** Shared scancode enums and abstract event types—extend here, don't duplicate translations.
+
+## Feature & cfg discipline
+
+- Feature flags live in root `Cargo.toml`. Gate OS-specific modules with tight cfgs (e.g., `cfg(all(unix, feature = "layer_shell", not(target_os = "macos")))`).
+- Prefer module-level gating over per-function cfgs to avoid empty stubs.
+- New backends: add feature in `Cargo.toml`, create gated module, log backend selection.
+
+## Async patterns
+
+- Tokio runtime with `futures` streams and `async_trait`. Model new flows as streams or async methods.
+- Avoid blocking; use `spawn_blocking` if needed. Prefer existing single-threaded stream handling.
+- `InputCapture` implements `Stream` and manually pumps backends—don't short-circuit this logic.
+
+## Commands
+
+```sh
+cargo build --workspace                                    # full build
+cargo build -p <crate>                                     # single crate
+cargo test --workspace                                     # all tests
+cargo fmt && cargo clippy --workspace --all-targets --all-features  # lint
+RUST_LOG=lan_mouse=debug cargo run                         # debug logging
+```
+
+Run from repo root—no `cd` in scripts.
+
+## Testing
+
+- Unit tests for utilities; integration tests for protocol behavior.
+- OS-specific backends: test via GTK/CLI on target OS or document manual verification.
+- Dummy backend exercises pipeline without real dependencies.
+- Verify `terminate()` releases keys on unexpected disconnect.
+
+## Workflow
+
+1. Clarify ambiguous requirements, especially OS-specific behavior.
+2. Implement minimal change; flag follow-up work.
+3. Add proportional tests; run `cargo test` on affected crates.
+4. Run `cargo fmt` and `cargo clippy --workspace --all-targets --all-features`.