Ownership: show borrow origin for active-borrow conflicts

[itsfuad]

Summary

Improve ownership diagnostics for borrow conflicts (T0037) by tracking borrow origin on owner state and emitting a secondary "borrow created here" label directly from owner metadata.

What changed

• Moved active borrow-origin tracking to owner-side state (activeBorrowLoc) in ownership value scope state.
• Updated bind/release/merge paths to keep owner-side borrow origin metadata accurate.
• Simplified conflict reporting path to look up owner directly instead of reverse-scanning borrower entries.
• Kept location normalization so labels always carry file info when available.
• Added regression test fixture under tests/repro/borrow_conflict_active_borrow_label.fer.

Validation

• go test ./internal/analysis/semantics/ownership -count=1
• Manual repro with ferret run tests/repro/borrow_conflict_active_borrow_label.fer shows:
  • secondary label: borrow created here
  • primary label: cannot use value while a mutable borrow is live

Notes

No pass-through wrappers added. Changes stay scoped to ownership analysis and diagnostics behavior.