Add task timer / deadline feature within an active work session

[ArsalanAnwer0]

Add the ability for users to start a task timer inside an active work session.

This should be separate from dev start, since work sessions represent time spent, while tasks represent goals or deadlines.

Example usage:

dev start
dev task start --time 3h

This allows users to give themselves a time limit (e.g. 3 hours, 8 hours) while working.

Users must have an active work session to start a task timer

Task timers accept human-friendly durations (e.g. 30m, 3h, 8h)

A task has: start time and expected duration (deadline)

Future commands may show: time remaining and overdue status

• New dev task command group

• dev task start --time starts a task timer

• Error if no active work session exists

• Task logic is separate from work session logic

• Designed to be extensible (pause, status, stop in future)

Notes

• This feature is intended to help users manage focus and deadlines, not replace work session tracking.