Run --update should re-register cron entries after downloading the latest release

[ChaseFlorell]

Problem

Currently, --update downloads the latest stream.py from GitHub but does not re-register cron entries afterward. This means that if the cron schedule in config.toml has been changed (either manually or by a previous --set-property call), the live crontab is never updated to reflect those changes.

Expected Behavior

After --update successfully downloads and installs the new release, it should:

1. Read the current config.toml (which may contain updated cron schedule values)
2. Call register_cron_entries(config) to sync the live crontab with whatever is in config.toml

This ensures that a user who edits their cron schedule in config.toml and then runs --update (or has cron.autoUpdate = true) gets the schedule applied automatically, without needing to also run --install or crontab -e by hand.

Example Scenario

A user has cron.autoUpdate = true so --update fires daily at midnight. They edit config.toml to change cron.start from 30 6 1-31 4-10 * to 0 7 1-31 4-10 *. The next midnight --update run downloads the latest release, but the crontab is still firing at 6:30 am. The user has to remember to re-run --install to actually apply the schedule change.

Proposed Fix

At the end of the --update flow, after the new stream.py has been written to disk, add a call to register_cron_entries(config) so the crontab is always in sync with config.toml post-update.

[dax-agent]

Acceptance Criteria

This issue will be considered complete when:

• After --update downloads and installs the new stream.py, it calls register_cron_entries(config) to sync the live crontab with config.toml
• A user who changes cron schedule values in config.toml and then runs --update sees the updated schedule reflected immediately — no manual --install or crontab -e required
• The existing cron.autoUpdate = true flow also applies the updated schedule on its daily run
• All new behaviour is covered by automated tests
• Existing tests continue to pass

[dax-agent]

Architecture

After stream.py is downloaded and written to disk during --update, call register_cron_entries(config).

Implementation

In the --update flow (likely in stream.py), after the download-and-replace logic completes successfully:

# Pseudocode - locate where stream.py is written, then:
register_cron_entries(config)

Why this works

• config is already loaded earlier in the update flow (needed to determine cron schedule for auto-update)
• register_cron_entries(config) already exists and handles reading the current crontab, computing diffs, and applying changes
• No new patterns or abstractions needed — this is a straightforward state-sync operation

Risks & Mitigations

• Risk: If register_cron_entries fails after file replacement, the system is left in a broken state.
  • Mitigation: Keep the existing error handling. The update should fail fast if cron registration fails.
• Risk: User who does not want cron behavior changed.
  • Mitigation: The function only writes to crontab if the schedule in config.toml differs from current crontab — idempotent operation.

Test cases (per acceptance criteria)

1. --update with modified cron schedule in config.toml → crontab reflects change
2. --update with unchanged schedule → crontab remains identical (idempotent)
3. cron.autoUpdate = true daily run with config change → schedule applied automatically
4. Existing tests continue to pass (no regression)
5. New test: verify register_cron_entries is called during update