fix(build): commit the datespec-move wiring (orphaned in T2c)

The T2c commit moved datespec.rs into hephd but left its wiring uncommitted:
hephd's lib never exported `pub mod datespec`, hephd lacked the chrono dep,
and the CLI still declared `mod datespec` for a file that had moved. The
working tree had these (so local builds passed) but the pushed tree didn't,
breaking `cargo install` of heph + heph-tui. Commit them.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -1286,6 +1286,7 @@ dependencies = [
  "anyhow",
  "axum",
  "base64",
+ "chrono",
  "clap",
  "fs4",
  "heph-core",

crates/heph/src/main.rs

@@ -13,9 +13,8 @@ use clap::{Parser, Subcommand};
 use serde_json::{json, Value};
 
 use heph_core::{Node, RankedTask, Task};
-use hephd::{default_socket_path, Client, DeviceFlow, KeyringTokenStore, TokenStore};
+use hephd::{datespec, default_socket_path, Client, DeviceFlow, KeyringTokenStore, TokenStore};
 
-mod datespec;
 mod service;
 
 #[derive(Parser, Debug)]

crates/hephd/Cargo.toml

@@ -18,6 +18,7 @@ path = "src/main.rs"
 
 [dependencies]
 heph-core = { path = "../heph-core" }
+chrono.workspace = true
 tokio.workspace = true
 serde.workspace = true
 serde_json.workspace = true

crates/hephd/src/datespec.rs

@@ -1,7 +1,8 @@
-//! Human-friendly date and recurrence parsing for the CLI (tech-spec §1, §8).
+//! Human-friendly date and recurrence parsing for client surfaces — the CLI
+//! and the TUI (tech-spec §1, §8, §8.1).
 //!
-//! `heph-core` is clock-pure (no ambient wall-clock reads); the CLI is a client,
-//! so it may read the local clock. Date parsing is split so the logic is
+//! `heph-core` is clock-pure (no ambient wall-clock reads); clients may read the
+//! local clock. Date parsing is split so the logic is
 //! deterministically testable: the pure functions take `today` / a year, and the
 //! thin wrappers supply `Local::now()`.
 //!

crates/hephd/src/lib.rs

@@ -10,6 +10,7 @@
 pub mod auth;
 pub mod client;
 pub mod clock;
+pub mod datespec;
 pub mod lock;
 pub mod oauth;
 pub mod remote;