Refactor: unify two-phase dispatch with per-core pending awareness

Replace the separate idle-dispatch and AIC-only pending-dispatch loops
with a single dispatch_shape() that iterates IDLE then PENDING phases
for every resource shape (AIC, AIV, MIX).

Key changes:
- Add CoreTracker::DispatchPhase enum and get_dispatchable_cores() as
  a unified query for both phases
- Rename get_idle_cluster_offset_states -> get_idle_core_offset_states;
  skip AIC-centric pending_occupied filter for AIV/MIX (fixes a latent
  bug where running+pending AIC blocked AIV idle dispatch)
- Consolidate get_pending_only_cluster_offset_states into
  get_pending_core_offset_states, extending pending dispatch to AIV
  and MIX shapes
- MIX pending dispatch: require at least one running core per cluster
  but allow idle cores to participate; dispatch_mix_block_to_cluster
  resolves per-core to_pending (idle cores use to_pending=false to
  trigger change_core_state, running cores use to_pending=true)
- Rename dispatch_block_to_cluster -> dispatch_block with a to_pending
  parameter; AIV pending dispatch passes resolved core bit offset
- Fix infinite spin when all tasks in a pending-phase batch are
  sync_start (requeued without dispatching); dispatch_shape now breaks
  when dispatched_any is false

Author: zhusy54