Include mention context in acp-based native agent (#36006)

Also adds data-layer support for symbols, thread, and rules.

Release Notes:

- N/A

---------

Co-authored-by: Cole Miller <cole@zed.dev>

crates/acp_thread/src/mention.rs

@@ -0,0 +1,122 @@
+use agent_client_protocol as acp;
+use anyhow::{Result, bail};
+use std::path::PathBuf;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum MentionUri {
+    File(PathBuf),
+    Symbol(PathBuf, String),
+    Thread(acp::SessionId),
+    Rule(String),
+}
+
+impl MentionUri {
+    pub fn parse(input: &str) -> Result<Self> {
+        let url = url::Url::parse(input)?;
+        let path = url.path();
+        match url.scheme() {
+            "file" => {
+                if let Some(fragment) = url.fragment() {
+                    Ok(Self::Symbol(path.into(), fragment.into()))
+                } else {
+                    Ok(Self::File(path.into()))
+                }
+            }
+            "zed" => {
+                if let Some(thread) = path.strip_prefix("/agent/thread/") {
+                    Ok(Self::Thread(acp::SessionId(thread.into())))
+                } else if let Some(rule) = path.strip_prefix("/agent/rule/") {
+                    Ok(Self::Rule(rule.into()))
+                } else {
+                    bail!("invalid zed url: {:?}", input);
+                }
+            }
+            other => bail!("unrecognized scheme {:?}", other),
+        }
+    }
+
+    pub fn name(&self) -> String {
+        match self {
+            MentionUri::File(path) => path.file_name().unwrap().to_string_lossy().into_owned(),
+            MentionUri::Symbol(_path, name) => name.clone(),
+            MentionUri::Thread(thread) => thread.to_string(),
+            MentionUri::Rule(rule) => rule.clone(),
+        }
+    }
+
+    pub fn to_link(&self) -> String {
+        let name = self.name();
+        let uri = self.to_uri();
+        format!("[{name}]({uri})")
+    }
+
+    pub fn to_uri(&self) -> String {
+        match self {
+            MentionUri::File(path) => {
+                format!("file://{}", path.display())
+            }
+            MentionUri::Symbol(path, name) => {
+                format!("file://{}#{}", path.display(), name)
+            }
+            MentionUri::Thread(thread) => {
+                format!("zed:///agent/thread/{}", thread.0)
+            }
+            MentionUri::Rule(rule) => {
+                format!("zed:///agent/rule/{}", rule)
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_mention_uri_parse_and_display() {
+        // Test file URI
+        let file_uri = "file:///path/to/file.rs";
+        let parsed = MentionUri::parse(file_uri).unwrap();
+        match &parsed {
+            MentionUri::File(path) => assert_eq!(path.to_str().unwrap(), "/path/to/file.rs"),
+            _ => panic!("Expected File variant"),
+        }
+        assert_eq!(parsed.to_uri(), file_uri);
+
+        // Test symbol URI
+        let symbol_uri = "file:///path/to/file.rs#MySymbol";
+        let parsed = MentionUri::parse(symbol_uri).unwrap();
+        match &parsed {
+            MentionUri::Symbol(path, symbol) => {
+                assert_eq!(path.to_str().unwrap(), "/path/to/file.rs");
+                assert_eq!(symbol, "MySymbol");
+            }
+            _ => panic!("Expected Symbol variant"),
+        }
+        assert_eq!(parsed.to_uri(), symbol_uri);
+
+        // Test thread URI
+        let thread_uri = "zed:///agent/thread/session123";
+        let parsed = MentionUri::parse(thread_uri).unwrap();
+        match &parsed {
+            MentionUri::Thread(session_id) => assert_eq!(session_id.0.as_ref(), "session123"),
+            _ => panic!("Expected Thread variant"),
+        }
+        assert_eq!(parsed.to_uri(), thread_uri);
+
+        // Test rule URI
+        let rule_uri = "zed:///agent/rule/my_rule";
+        let parsed = MentionUri::parse(rule_uri).unwrap();
+        match &parsed {
+            MentionUri::Rule(rule) => assert_eq!(rule, "my_rule"),
+            _ => panic!("Expected Rule variant"),
+        }
+        assert_eq!(parsed.to_uri(), rule_uri);
+
+        // Test invalid scheme
+        assert!(MentionUri::parse("http://example.com").is_err());
+
+        // Test invalid zed path
+        assert!(MentionUri::parse("zed:///invalid/path").is_err());
+    }
+}