Add multi-base chain modelling, fix price-band-aware demand/supply, tranche-split sell tool

- puga/network.py + tools/network.py: model a multi-base chain (e.g. mine LST at one base,
  ship it, consume it at another). Simulates each base independently, nets a transferred
  material's producer-surplus against consumer-need, charges real freight only on what's
  moved, cm_free for a founding covered by a Core Module Kit. Worked example in plans/chains/.
- puga/saturation.py: real price-band filtering. FIO's order_book NarrowPriceBandLow/High and
  WidePriceBandLow/High match APEX's own displayed Price Band exactly (verified live) - an
  order outside it is a stale artifact, not just uncompetitive. Added in_band() and
  effective_demand(); effective_supply() gained the same hard band filter alongside its
  existing soft vwap-proximity filter (renamed that param mult to free up `band`). Wired into
  tools/scan.py stage 2 in place of the raw, unfiltered demand figure. Was flagged as an
  unimplemented refinement in saturation-design.md since the original design review.
- tools/sell.py: self-contained tranche split (aggressive tranche capped at a volume quantile,
  median normally or 80th pct with --tight when a payment is imminent and stockout risk
  outweighs margin; patient tranche priced under the next competitor tier). Instant-bid
  comparison moved behind --show-bid (off by default).
- Docs and roadmap updated accordingly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

puga/saturation.py

@@ -48,9 +48,30 @@ def p_patient(asks: list[tuple[float, float]], tr: float, produced_per_day: floa
     return max(bid, min(p, hi))
 
 
-def effective_supply(asks: list[tuple[float, float]], ref_price: float | None, band: float = 1.25) -> float:
-    """Units of standing sell orders that actually compete: price <= band x reference (vwap7 or ask).
-    Stale asks far above market (e.g. 1500 units at 1.5x vwap) are not competition. asks = [(price, units)]."""
+def in_band(price: float, band: tuple[float | None, float | None] | None) -> bool:
+    """band = (low, high), the exchange's tradeable Price Band (FIO order_book's Narrow/WidePriceBandLow/High;
+    verified live 2026-09-25 to match APEX's own displayed 'Price Band' field exactly). An order outside it is
+    not just uncompetitive, it is not currently placeable at all, and existing ones there are stale artifacts
+    (e.g. a leftover 334 AIC bid sitting under a 663 floor) that will never fill; not just a heuristic cutoff."""
+    if not band:
+        return True
+    lo, hi = band
+    return (lo is None or price >= lo) and (hi is None or price <= hi)
+
+
+def effective_supply(asks: list[tuple[float, float]], ref_price: float | None, mult: float = 1.25,
+                     band: tuple[float | None, float | None] | None = None) -> float:
+    """Units of standing sell orders that actually compete: in the tradeable price band (hard filter, if given)
+    AND price <= mult x reference (vwap7 or ask; soft filter for "active competition" vs merely valid-but-stale
+    high asks like OCK's top tier). asks = [(price, units)]."""
+    asks = [(p, u) for p, u in asks if in_band(p, band)]
     if not ref_price:
         return sum(u for _, u in asks)
-    return sum(u for p, u in asks if p <= band * ref_price)
+    return sum(u for p, u in asks if p <= mult * ref_price)
+
+
+def effective_demand(bids: list[tuple[float, float]], band: tuple[float | None, float | None] | None) -> float:
+    """Units of standing buy orders that are actually tradeable: within the exchange's price band. Filters out
+    stale/abandoned bids placed under a different band or long since left behind by the market (e.g. a 334 AIC
+    bid when the floor is 663) rather than genuine, fillable demand. bids = [(price, units)]."""
+    return sum(u for p, u in bids if in_band(p, band))