agent: a plugin on the new SDK (agent.chat, tools call/read_file/write_file/list_dir/copy_dir)

Holds the history lock for a turn, 600 s grace period, interim texts as
core.notify. Tests with a fake LLM in the real core. The SDK tests of
/proc, /self, /run, and detached notifications now run.

cli/tests/sdk.rs

@@ -157,7 +157,6 @@ async fn discovery_is_compatible() {
 }
 /// Detached SDK calls receive progress and forward it through core.notify.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-#[ignore = "core: stdout response can overtake a preceding core.notify"]
 async fn detached_call_notifications() {
     let world = TestWorld::new();
     let host = world.start().await;
@@ -229,7 +228,6 @@ async fn world_endpoint() {
 }
 /// The HTTP example exposes its self endpoint through the process namespace.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-#[ignore = "needs /proc, /self, and /run (T6)"]
 async fn www_control_through_proc() {
     let world = TestWorld::new();
     let host = world.start().await;
@@ -241,7 +239,6 @@ async fn www_control_through_proc() {
 }
 /// The vault example publishes a fixed endpoint in the shared run namespace.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-#[ignore = "needs /proc, /self, and /run (T6)"]
 async fn secrets_fixed_endpoint() {
     let world = TestWorld::new();
     let host = world.start().await;