Add hooks, @file mentions, session search/fork/export, follow-scroll

- Hooks ([[hooks]]): pre_tool, post_tool, user_prompt, stop; sandboxed, exit 2 blocks
- @file mentions with autocomplete; mentioned files/folders are attached to the prompt
- Session full-text search in the sidebar, fork into a copy, export as Markdown/JSON
- Chat follows the newest message until the user scrolls up; jump-to-latest button
- SVG activity spark and thinking icon instead of Unicode/emoji glyphs
- File search ranks name matches first and returns relative paths

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/src/export.rs

@@ -0,0 +1,83 @@
+//! Session export as Markdown.
+
+use crate::types::{Message, Part, Role, Session};
+
+fn fence(s: &str) -> String {
+    // A fence longer than any backtick run inside the content.
+    let mut longest = 0;
+    let mut run = 0;
+    for c in s.chars() {
+        if c == '`' {
+            run += 1;
+            longest = longest.max(run);
+        } else {
+            run = 0;
+        }
+    }
+    "`".repeat((longest + 1).max(3))
+}
+
+fn clip(s: &str, max: usize) -> String {
+    if s.len() <= max {
+        return s.to_string();
+    }
+    let mut end = max;
+    while !s.is_char_boundary(end) {
+        end -= 1;
+    }
+    format!("{}\n… ({} more bytes)", &s[..end], s.len() - end)
+}
+
+fn time(ms: i64) -> String {
+    chrono::DateTime::from_timestamp_millis(ms).map(|t| t.format("%Y-%m-%d %H:%M UTC").to_string()).unwrap_or_default()
+}
+
+pub fn markdown(s: &Session, messages: &[Message]) -> String {
+    let title = if s.title.is_empty() { "Untitled session" } else { s.title.as_str() };
+    let mut out = format!(
+        "# {title}\n\n- Directory: `{}`\n- Model: `{}`\n- Mode: {}\n- Created: {}\n- Exported from CodeCraft\n\n---\n\n",
+        s.cwd,
+        s.model,
+        s.agent,
+        time(s.created_at)
+    );
+    for m in messages {
+        let is_tool_results = m.parts.iter().all(|p| matches!(p, Part::ToolResult { .. }));
+        if !is_tool_results {
+            let who = match m.role {
+                Role::User => "User".to_string(),
+                _ => format!("Assistant{}", m.model.as_deref().map(|x| format!(" ({x})")).unwrap_or_default()),
+            };
+            out.push_str(&format!("## {who} · {}\n\n", time(m.created_at)));
+        }
+        for p in &m.parts {
+            match p {
+                Part::Text { text } => out.push_str(&format!("{}\n\n", text.trim())),
+                Part::Summary { text } => out.push_str(&format!("<details><summary>Summary of the earlier conversation</summary>\n\n{}\n\n</details>\n\n", text.trim())),
+                Part::Reasoning { text, .. } if !text.trim().is_empty() => {
+                    out.push_str(&format!("<details><summary>Thinking</summary>\n\n{}\n\n</details>\n\n", text.trim()))
+                }
+                Part::Reasoning { .. } => {}
+                Part::Image { image } => out.push_str(&format!("*[image: {}]*\n\n", image.media_type)),
+                Part::ToolCall { name, input, .. } => {
+                    let body = match name.as_str() {
+                        "bash" => input["command"].as_str().unwrap_or("").to_string(),
+                        _ => serde_json::to_string_pretty(input).unwrap_or_default(),
+                    };
+                    let body = clip(&body, 4000);
+                    let f = fence(&body);
+                    out.push_str(&format!("**Tool `{name}`**\n\n{f}{}\n{body}\n{f}\n\n", if name == "bash" { "sh" } else { "json" }));
+                }
+                Part::ToolResult { name, content, is_error, .. } => {
+                    let body = clip(content.trim(), 4000);
+                    let f = fence(&body);
+                    out.push_str(&format!(
+                        "<details><summary>{} of <code>{name}</code></summary>\n\n{f}\n{body}\n{f}\n\n</details>\n\n",
+                        if *is_error { "Error" } else { "Result" }
+                    ));
+                }
+            }
+        }
+    }
+    out
+}