Automatic update-check never fires; version cache only refreshes via explicit `td version`

[pjsvis]

Environment:

• td: 0.51.0 (Homebrew, marcus/tap)
• OS: macOS 15, arm64 (Tahoe)
• Install: brew install marcus/tap/td

Summary:

The version cache at ~/.config/td/version_cache.json is only refreshed by the explicit td version command. Normal usage (td status, td list, td create, td --version, etc.) does not trigger any automatic update check. As a result, hasUpdate can report false with a stale latestVersion for months, and users are never prompted that a new release is available.

Reproduction (confirmed on 0.51.0):

1. cat ~/.config/td/version_cache.json — note checkedAt and currentVersion.
2. Run several normal commands: td status, td list, td --version.
3. Re-read the cache. checkedAt is unchanged.
4. Run td version.
5. Re-read the cache. checkedAt and currentVersion now update to the present.

Observed evidence:

My cache had been stuck since 2026-02-23:

{
  "latestVersion": "v0.38.0",
  "currentVersion": "0.38.0",
  "checkedAt": "2026-02-23T11:30:46.139516Z",
  "hasUpdate": false
}

This persisted through 4+ months of daily use and two upgrades (0.49.0 and 0.51.0), always reporting hasUpdate: false with latestVersion 0.38.0 — so no update was ever surfaced. After running td version on 0.51.0, the cache correctly updated to:

{
  "latestVersion": "v0.51.0",
  "currentVersion": "0.51.0",
  "checkedAt": "2026-07-09T06:34:56.403581+01:00",
  "hasUpdate": false
}

Expected:

An automatic, periodic update check during normal usage so the cache (and any update prompt) reflects reality without requiring the user to remember td version.

Actual:

Only td version performs a check; no automatic check fires, so a stale hasUpdate: false can persist indefinitely.

Impact:

New releases go unnoticed. The 0.49.0 → 0.51.0 release (which fixes an td epic create --description flag bug) was not surfaced here; the upgrade was only applied manually after noticing the formula had advanced.

Question:

Is the automatic check intended to be periodic/throttled, and is there a config option to enable or tune it? If it is intended to fire during normal usage, it does not appear to be triggering on this setup.