feat: add stderr progress + timing summaries for import and connector sync

[hurttlocker]

Implements #292.

What shipped

cortex import

• Added periodic stderr progress lines during file import:
  • import progress: <current>/<total> files (<filename>)
• Added periodic stderr extraction progress during --extract:
  • extraction progress: <done>/<total> memories, <facts> facts
• Added final stderr timing summary:
  • files scanned/imported/skipped
  • total facts extracted
  • total duration

cortex connect sync

• Added per-provider progress callback plumbing in internal/connect/sync.go.
• CLI now emits periodic stderr progress lines per provider:
  • sync progress [provider]: <current>/<total> records (imported=..., skipped=...)
• Added final stderr timing summary for:
  • --all (aggregate counts + duration)
  • --provider <name> (provider counts + duration)

Design goals met

• ✅ Progress output goes to stderr (stdout remains clean for piping)
• ✅ No spinner requirement; newline progress is used
• ✅ Includes counters requested for import + connect sync
• ✅ Includes final timing summary

Validation

• go test ./internal/connect ./cmd/cortex -run 'Progress|Import|Connect' -v ✅
• go test ./... ✅