## Summary
Adds execution-window product surfaces for both declarative and
imperative schedules.
- Declarative schedules can set `window` through `schedules.task()`,
with support for whole-minute, hour, and percentage values.
- Imperative schedules can create, update, clear, and inspect windows
through the API and dashboard.
- Schedule API responses preserve `nextRun` as the nominal CRON time and
expose `nextRunEffectiveAt` as the stable assigned time.
- The dashboard displays configured windows alongside assigned
upcoming-run times.
- Deploy output summarizes declarative schedules and suggests adding a
wider window when the default 60-second placement range is used.
## Design
Window validation remains authoritative on the server and ensures each
window is compatible with the schedule cadence. Omitting a window uses
the default 60-second range, while explicit zero-duration windows remain
supported.
Deployment summaries are derived from the deployment's stored task
metadata, so they reflect the declarations associated with that
deployment.
- New DB fields on Schedule and ScheduleInstance
- Use `queueTimestamp` for the "effectiveAt" delayed start time,
propagate it to Clickhouse TaskRun table
- Disable fastpath for delayed jobs
- Add schedule timing logic, API endpoints with windows, persistence
- Calculate phase for every schedule, only persist when window is
non-null
- Additional o11y for phased rollout
Chris Arderne