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/sse.rs

@@ -0,0 +1,128 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct SseEvent {
+    pub event: Option<String>,
+    pub data: String,
+    pub id: Option<String>,
+    pub retry: Option<u64>,
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct IncrementalSseParser {
+    buffer: String,
+    event_name: Option<String>,
+    data_lines: Vec<String>,
+    id: Option<String>,
+    retry: Option<u64>,
+}
+
+impl IncrementalSseParser {
+    #[must_use]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn push_chunk(&mut self, chunk: &str) -> Vec<SseEvent> {
+        self.buffer.push_str(chunk);
+        let mut events = Vec::new();
+
+        while let Some(index) = self.buffer.find('\n') {
+            let mut line = self.buffer.drain(..=index).collect::<String>();
+            if line.ends_with('\n') {
+                line.pop();
+            }
+            if line.ends_with('\r') {
+                line.pop();
+            }
+            self.process_line(&line, &mut events);
+        }
+
+        events
+    }
+
+    pub fn finish(&mut self) -> Vec<SseEvent> {
+        let mut events = Vec::new();
+        if !self.buffer.is_empty() {
+            let line = std::mem::take(&mut self.buffer);
+            self.process_line(line.trim_end_matches('\r'), &mut events);
+        }
+        if let Some(event) = self.take_event() {
+            events.push(event);
+        }
+        events
+    }
+
+    fn process_line(&mut self, line: &str, events: &mut Vec<SseEvent>) {
+        if line.is_empty() {
+            if let Some(event) = self.take_event() {
+                events.push(event);
+            }
+            return;
+        }
+
+        if line.starts_with(':') {
+            return;
+        }
+
+        let (field, value) = line.split_once(':').map_or((line, ""), |(field, value)| {
+            let trimmed = value.strip_prefix(' ').unwrap_or(value);
+            (field, trimmed)
+        });
+
+        match field {
+            "event" => self.event_name = Some(value.to_owned()),
+            "data" => self.data_lines.push(value.to_owned()),
+            "id" => self.id = Some(value.to_owned()),
+            "retry" => self.retry = value.parse::<u64>().ok(),
+            _ => {}
+        }
+    }
+
+    fn take_event(&mut self) -> Option<SseEvent> {
+        if self.data_lines.is_empty() && self.event_name.is_none() && self.id.is_none() && self.retry.is_none() {
+            return None;
+        }
+
+        let data = self.data_lines.join("\n");
+        self.data_lines.clear();
+
+        Some(SseEvent {
+            event: self.event_name.take(),
+            data,
+            id: self.id.take(),
+            retry: self.retry.take(),
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{IncrementalSseParser, SseEvent};
+
+    #[test]
+    fn parses_streaming_events() {
+        let mut parser = IncrementalSseParser::new();
+        let first = parser.push_chunk("event: message\ndata: hel");
+        assert!(first.is_empty());
+
+        let second = parser.push_chunk("lo\n\nid: 1\ndata: world\n\n");
+        assert_eq!(
+            second,
+            vec![
+                SseEvent {
+                    event: Some(String::from("message")),
+                    data: String::from("hello"),
+                    id: None,
+                    retry: None,
+                },
+                SseEvent {
+                    event: None,
+                    data: String::from("world"),
+                    id: Some(String::from("1")),
+                    retry: None,
+                },
+            ]
+        );
+    }
+}