feat: add search term to thread list (#12578)

Add `searchTerm` to `thread/list` that will search for a match in the
titles (the condition being `searchTerm` $$\in$$ `title`)

codex-rs/app-server/Cargo.toml

@@ -65,6 +65,7 @@ axum = { workspace = true, default-features = false, features = [
 base64 = { workspace = true }
 codex-execpolicy = { workspace = true }
 core_test_support = { workspace = true }
+codex-state = { workspace = true }
 codex-utils-cargo-bin = { workspace = true }
 os_info = { workspace = true }
 pretty_assertions = { workspace = true }