feat: Rust port of Claude Code CLI

Crates:
- api: Anthropic Messages API client with SSE streaming
- tools: Claude-compatible tool implementations (Bash, Read, Write, Edit, Glob, Grep + extended suite)
- runtime: conversation loop, session persistence, permissions, system prompt builder
- rusty-claude-cli: terminal UI with markdown rendering, syntax highlighting, spinners
- commands: subcommand definitions
- compat-harness: upstream TS parity verification

All crates pass cargo fmt/clippy/test.

rust/crates/api/src/lib.rs

@@ -0,0 +1,13 @@
+mod client;
+mod error;
+mod sse;
+mod types;
+
+pub use client::{AnthropicClient, MessageStream};
+pub use error::ApiError;
+pub use sse::{parse_frame, SseParser};
+pub use types::{
+    ContentBlockDelta, ContentBlockDeltaEvent, ContentBlockStartEvent, ContentBlockStopEvent,
+    InputContentBlock, InputMessage, MessageRequest, MessageResponse, MessageStartEvent,
+    MessageStopEvent, OutputContentBlock, StreamEvent, Usage,
+};