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/runtime/src/lib.rs

@@ -0,0 +1,20 @@
+mod bootstrap;
+mod conversation;
+mod json;
+mod permissions;
+mod prompt;
+mod session;
+
+pub use bootstrap::{BootstrapPhase, BootstrapPlan};
+pub use conversation::{
+    ApiClient, ApiRequest, AssistantEvent, ConversationRuntime, RuntimeError, StaticToolExecutor,
+    ToolError, ToolExecutor, TurnSummary,
+};
+pub use permissions::{
+    PermissionMode, PermissionOutcome, PermissionPolicy, PermissionPromptDecision,
+    PermissionPrompter, PermissionRequest,
+};
+pub use prompt::{
+    prepend_bullets, SystemPromptBuilder, FRONTIER_MODEL_NAME, SYSTEM_PROMPT_DYNAMIC_BOUNDARY,
+};
+pub use session::{ContentBlock, ConversationMessage, MessageRole, Session, SessionError};