#300 feat(rules): merge quiet-watchers into periodic-updates

quiet-watchers was three sentences about how a watcher reports, and periodic-updates already covers the same watchers (its changelog entry says the two fit together). Folding it in removes one optional rule and one install choice: periodic-updates now also says to arm a watcher to report in full only a milestone, failure, stall, forecast change or completion, and that an event that changes nothing gets at most one line.

A configuration that lists quiet-watchers now fails with unknown modifier, so remove it from such a configuration. Nothing else in the repository referenced the rule.

Checks: node --test 136 pass, oxfmt clean, check:package ok.

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Summary by cubic

Merges the quiet-watchers modifier into periodic-updates so watcher reporting behaves the same under one optional rule instead of two.

• periodic-updates now also says to arm a watcher to report in full only a milestone, failure, stall, forecast change, or completion, and that an event that changes nothing gets at most one line.
• Removes the quiet-watchers rule, its README entry, and its install choice.

Migration

• A configuration that lists quiet-watchers now fails with unknown modifier; remove it from such a configuration.

Summary by CodeRabbit

• Updates
  • The periodic-updates option now limits watcher events with no changes to at most one line. Watchers still report milestones, failures, stalls, forecast changes, and completed runs in full.
  • For jobs expected to run longer than about 10 minutes, updates continue every five minutes by default. Without a background watcher or timer, updates appear at the first natural checkpoint after each interval.
  • Configurations that list quiet-watchers must remove it; its no-change reporting behavior is now covered by periodic-updates.