Add egui_kittest_mcp server

New binary crate that exposes an MCP (Model Context Protocol) server backed by
the `egui_inspection` protocol. The server bridges a running egui peer — a
spawned `egui_kittest` harness child process or an attached live `eframe` app —
to MCP tool handlers that drive it.

Components:
- `bridge.rs`: spawns / attaches a peer over a unix socket, runs reader+writer
  Tokio tasks that pump `HarnessMessage` ↔ `InspectorCommand` and track the
  peer's `Hello`, latest frame, accesskit tree, and blocked / finished state.
- `tools.rs`: `rmcp`-derived tool router with commands for stepping, event
  injection (click / type / scroll / hover / drag / keys), resizing, screenshot
  capture, accesskit tree queries, and lifecycle (launch / attach / kill).
- `tree.rs`: accesskit-tree projection helpers shared by the tools.
- `shim.rs` / `main.rs`: shim role that lets the same binary act as the child
  inspector for kittest harnesses, relaying bytes between the harness stdio
  and the MCP server's unix socket.
- `server.rs`: rmcp stdio entry point.

Live-app example added at `examples/egui_mcp/`.

examples/egui_mcp/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "egui_mcp"
+version = "0.1.0"
+authors = ["Lucas Meurer <hi@lucasmerlin.me>"]
+license = "MIT OR Apache-2.0"
+edition = "2024"
+rust-version = "1.92"
+publish = false
+
+[lints]
+workspace = true
+
+
+[dependencies]
+egui = { workspace = true, features = ["default"] }
+egui_demo_lib = { workspace = true, features = ["default"] }
+egui_kittest = { workspace = true, features = ["wgpu", "inspector"] }