Lay the groundwork to support history in agent2 (#36483)

This pull request introduces title generation and history replaying. We
still need to wire up the rest of the history but this gets us very
close. I extracted a lot of this code from `agent2-history` because that
branch was starting to get long-lived and there were lots of changes
since we started.

Release Notes:

- N/A

crates/agent_servers/src/claude.rs

@@ -1,6 +1,7 @@
 mod mcp_server;
 pub mod tools;
 
+use action_log::ActionLog;
 use collections::HashMap;
 use context_server::listener::McpServerTool;
 use language_models::provider::anthropic::AnthropicLanguageModelProvider;
@@ -215,8 +216,15 @@ impl AgentConnection for ClaudeAgentConnection {
                 }
             });
 
-            let thread = cx.new(|cx| {
-                AcpThread::new("Claude Code", self.clone(), project, session_id.clone(), cx)
+            let action_log = cx.new(|_| ActionLog::new(project.clone()))?;
+            let thread = cx.new(|_cx| {
+                AcpThread::new(
+                    "Claude Code",
+                    self.clone(),
+                    project,
+                    action_log,
+                    session_id.clone(),
+                )
             })?;
 
             thread_tx.send(thread.downgrade())?;