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/Cargo.toml

@@ -18,6 +18,7 @@ doctest = false
 
 [dependencies]
 acp_thread.workspace = true
+action_log.workspace = true
 agent-client-protocol.workspace = true
 agent_settings.workspace = true
 agentic-coding-protocol.workspace = true

crates/agent_servers/src/acp/v0.rs

@@ -1,4 +1,5 @@
 // Translates old acp agents into the new schema
+use action_log::ActionLog;
 use agent_client_protocol as acp;
 use agentic_coding_protocol::{self as acp_old, AgentRequest as _};
 use anyhow::{Context as _, Result, anyhow};
@@ -443,7 +444,8 @@ impl AgentConnection for AcpConnection {
             cx.update(|cx| {
                 let thread = cx.new(|cx| {
                     let session_id = acp::SessionId("acp-old-no-id".into());
-                    AcpThread::new(self.name, self.clone(), project, session_id, cx)
+                    let action_log = cx.new(|_| ActionLog::new(project.clone()));
+                    AcpThread::new(self.name, self.clone(), project, action_log, session_id)
                 });
                 current_thread.replace(thread.downgrade());
                 thread

crates/agent_servers/src/acp/v1.rs

@@ -1,3 +1,4 @@
+use action_log::ActionLog;
 use agent_client_protocol::{self as acp, Agent as _};
 use anyhow::anyhow;
 use collections::HashMap;
@@ -153,14 +154,14 @@ impl AgentConnection for AcpConnection {
                 })?;
 
             let session_id = response.session_id;
-
-            let thread = cx.new(|cx| {
+            let action_log = cx.new(|_| ActionLog::new(project.clone()))?;
+            let thread = cx.new(|_cx| {
                 AcpThread::new(
                     self.server_name,
                     self.clone(),
                     project,
+                    action_log,
                     session_id.clone(),
-                    cx,
                 )
             })?;
 

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())?;