[codex] Add feature-gated time tools

Cargo.toml

@@ -52,12 +52,19 @@ rusqlite = { version = "0.40", features = ["bundled"], optional = true }
 # by the `repl` feature to keep the default build light.
 rhai = { version = "1", features = ["sync"], optional = true }
 
+# Optional builtin tool family for deterministic time/date helpers.
+chrono = { version = "0.4", optional = true }
+chrono-tz = { version = "0.10", optional = true }
+
 [features]
 default = []
 # Embedded SQLite-backed checkpointer (`graph::checkpoint::SqliteCheckpointer`).
 sqlite = ["dep:rusqlite"]
 # Embedded Rhai-backed `.ragsh` REPL session runtime (`repl::session`).
 repl = ["dep:rhai"]
+# Builtin generic tools (`harness::tools`) kept out of the default dependency
+# graph so host applications can choose whether they want these implementations.
+tools = ["dep:chrono", "dep:chrono-tz"]
 
 [dev-dependencies]
 tokio = { version = "1", features = ["macros", "rt-multi-thread", "time", "test-util"] }

src/harness/mod.rs

@@ -38,6 +38,8 @@ pub mod subagent;
 pub mod summarization;
 pub mod testkit;
 pub mod tool;
+#[cfg(feature = "tools")]
+pub mod tools;
 pub mod usage;
 pub mod workspace;
 

src/harness/tools/mod.rs

@@ -0,0 +1,13 @@
+//! Optional builtin harness tools.
+//!
+//! These tools are generic implementations that depend only on TinyAgents'
+//! [`Tool`][crate::harness::tool::Tool] interface. They are behind the `tools`
+//! Cargo feature so applications that provide their own tool surface do not pull
+//! in extra dependencies by default.
+
+mod time;
+
+pub use time::{CurrentTimeTool, ResolveTimeTool, register_time_tools, time_tools};
+
+#[cfg(test)]
+mod time_test;