Additive schedule registration for TypeScript for file-splitting

[JasonAtClockwork]

Closes: #4571 - The secondary issue specifically

Description of Changes

• New spacetime.schedule(table, reducerOrProcedure) API avoids forcing tables to import reducers
  • Fixes split table/reducer files creating circular TypeScript references with table({ scheduled })
• Kept the existing table({ scheduled }) path working
• Moved ScheduleAt column tracking onto table metadata
  • Lets the new schedule API resolve schedule-at columns without relying on legacy table options
  • Reuses the same schedule resolution path for legacy and new schedules

Other Options Considered

• Rust-inspired schedule token/name handle
  • Closest conceptual match to Rust: table stores a schedule descriptor/name and the reducer binds the implementation separately
  • Avoids importing reducers from table definitions and could preserve type checking if the token carries the row type
  • Adds more API surface and abstraction, and needs careful design to avoid users managing fragile names manually
• scheduled: 'reducerName' string/name in table(...)
  • Very simple and closest to the raw module-def storage model
  • Fully breaks the runtime import cycle
  • Loses compile-time signature checking unless paired with another checker/registration API, and typos become runtime/module validation errors
  • This basically is what we had before 2.0

API and ABI breaking changes

• Adds new TypeScript API: spacetime.schedule(table, reducerOrProcedure)
• No intended breaking changes to existing table({ scheduled }) behavior

Expected complexity level and risk

3 - Preserving legacy scheduled table behavior while changing how schedule metadata is assembled

Testing

• Added new tests to cover the legacy schedule and new registration
• Ran a local throwaway test project to test before and after for both legacy + new api