refactor(lifecycle): drive tasks through a phases handle

[jbedard]

TaskLifecycleTrait becomes Phases, and a task opens its _impl with ph = phases.new(ctx, data) instead of threading (ctx, lifecycle, data) through every call:

setup_phase(ctx, lifecycle, subject, kind, data, hc, bz, cmd)
    -> ph.setup(subject, kind, command = cmd)
task_update(ctx, lifecycle, status, progress, ...)
    -> ph.update(status, progress, ...)
dispatch_task_update(ctx, lifecycle, update)   -> ph.dispatch(update)
apply_repro_fix_hooks(ctx, lifecycle, data, ...)
    -> ph.suggest_fixes(kind, status, ...)

The records move behind the same namespace (phases.Update / .ProgressStyles / .Phase / .ReproFixCommand), so lifecycle.axl is a single import at the use site, and a task splats phases.TRAITS into its trait list. ph.reset(fresh) refills the held dict in place, which is what the Bazel retry loop needs between attempts.

traits.axl re-exports Phases for user config.axl files.

Changes are visible to end-users: no

Test plan

• Covered by existing test cases