"""Vendored surfer PoC (crypto cross-sectional momentum research sweep).

Provenance: copied verbatim from foxhunt `scripts/surfer/{signal_sweep,pit_sweep}.py`.

ONLY edits applied (no algorithm / math / constant changes):
  * `sys.path.insert(...)` + bare sibling imports rewritten as package-relative
    (`from fxhnt.vendor.surfer.signal_sweep import ...`, `from fxhnt.vendor.surfer import pit_sweep`).
  * data root made configurable via `$FXHNT_SURFER_DATA_DIR` (default `/data/surfer`):
    `pit_sweep.load()` reads `$FXHNT_SURFER_DATA_DIR/crypto_pit/*.npz`.

(The `surfer_poc` module — a value-returning `paper_step` refactor of `paper()` for a since-retired
ForwardTracker sleeve — was RETIRED along with its dormant caller; Phase 0b Task 7c.)

torch is imported at module level (used in `signal_sweep.sharpe_t`/`validate`) and is kept — this is a
faithful port, not a numpy reimplementation.
"""
