Add drawing tools, Mermaid support, and MCP server bridge

- Convert flat project to Cargo workspace (crates/agcanvas, crates/agcanvas-mcp)
- Add drawing layer: rectangles, ellipses, lines, arrows, text with select/move/resize
- Add Mermaid diagram rendering via mermaid-rs-renderer
- Add agcanvas-mcp: MCP server bridge for Claude Code, OpenCode, and Codex
- Add toolbar UI with keyboard shortcuts (V/R/E/L/A/T) and shape interaction
- Add example MCP configs for Claude Code, OpenCode, and Codex
- Update README with full feature docs, MCP setup, and updated architecture

Cargo.toml

@@ -1,48 +1,12 @@
-[package]
-name = "agcanvas"
+[workspace]
+members = ["crates/agcanvas", "crates/agcanvas-mcp"]
+resolver = "2"
+
+[workspace.package]
 version = "0.1.0"
 edition = "2021"
-description = "Interactive canvas for agent-human collaboration with SVG support"
 license = "MIT"
 
-[dependencies]
-# GUI
-eframe = { version = "0.29", default-features = false, features = [
-    "default_fonts",
-    "glow",
-    "persistence",
-] }
-egui = "0.29"
-egui_extras = { version = "0.29", features = ["image"] }
-
-# SVG parsing and rendering
-usvg = "0.44"
-resvg = "0.44"
-tiny-skia = "0.11"
-
-# Clipboard
-arboard = "3.4"
-
-# Serialization (for agent protocol)
-serde = { version = "1.0", features = ["derive"] }
-serde_json = "1.0"
-
-# Agent communication
-tokio = { version = "1.0", features = ["rt-multi-thread", "sync", "macros"] }
-tokio-tungstenite = "0.24"
-futures-util = "0.3"
-
-# Logging
-tracing = "0.1"
-tracing-subscriber = { version = "0.3", features = ["env-filter"] }
-
-# Error handling
-anyhow = "1.0"
-thiserror = "1.0"
-
-# Image handling for texture conversion
-image = { version = "0.25", default-features = false, features = ["png"] }
-
 [profile.release]
 opt-level = 3
 lto = true