feat: triggers without automation + flyte.run(trigger) to fire on demand

[kumare3]

Triggers no longer require an automation. A trigger without one is a named launch configuration (inputs, env vars, queue, notifications) that only fires on demand. flyte.run(trigger, ...) fires any deployed trigger from Python, as the trigger, so the run carries its registered config and is recorded as trigger-fired.

import flyte
import flyte.notify
import flyte.remote
from flyte.models import ActionPhase

env = flyte.TaskEnvironment(name="reports")

# No automation: nothing schedules this, it is fired on demand.
full_report = flyte.Trigger(
    name="full-report",
    inputs={"region": "all", "days": 30},
    env_vars={"REPORT_VERBOSE": "1"},
    notifications=flyte.notify.Email(on_phase=ActionPhase.SUCCEEDED, recipients=("me@example.com",)),
)

@env.task(triggers=(full_report,))
async def report(region: str = "all", days: int = 7) -> str:
    return f"report for {region!r} over {days} day(s)"

# Fire it programmatically, with the trigger's inputs / env vars / notifications.
trigger = flyte.remote.Trigger.get(name="full-report", task_name=report.name)
run = flyte.run(trigger)            # region="all", days=30
run = flyte.run(trigger, days=3)    # override one input, keep the rest

Also: flyte create trigger no longer requires --schedule. Examples in examples/triggers/manual.py and examples/triggers/programmatic.py.