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>

docs/roadmap.md

@@ -11,6 +11,7 @@ Legend: [ ] todo, [x] done. Build order matters; each step is usable on its own.
 6. [x] `tools/chain.py`: full bill of materials, make-vs-buy per node.
 7. [ ] `tools/whatif.py`: marginal ROI of adding a building to the actual state (uses `state/company.yaml`, efficiency stack, imports).
 8. [ ] `tools/planet.py`, `tools/found.py`: rank planets for a resource; founding cost including environment extras.
+13b. [x] `puga/network.py` + `tools/network.py`: multi-base chain modelling (per-base simulate, net transfers against real freight, `cm_free` for kits). Worked example: `plans/chains/nike_deimos_lst.yaml` (Nike LST -> Deimos PP2/BSE). Known gap: reports whole-plan profit per base, not the marginal addition; caller must diff manually.
 9. [ ] `tools/route.py`, `tools/haul.py`: jump graph, fuel, profit per trip.
 9b. [x] (dry-run default, --apply after user yes) `tools/plan_push.py`: create/update `[PuGa]` plans in PRUNplanner from YAML (Api-Key auth; see decisions.md for guardrails).
 10. [x] `tools/state.py sync` (sites, production efficiency, storage, ships, cash, permits): inventory, production, ships into `state/`.
@@ -25,3 +26,4 @@ Legend: [ ] todo, [x] done. Build order matters; each step is usable on its own.
 - PRUNplanner auth is known (`Authorization: Api-Key <key>`). FIO REST and FIO API are separate services with separate keys (separate services with separate keys; an earlier "one API" reading was wrong). Keys are in `.env`. Verified 2026-09-18: FIO_REST_KEY works on rest.fnar.net as `Authorization: <key>` (own /sites, /storage etc. readable); FIO_API_KEY gives 401 there, host unknown. PRUNplanner key works (plans 0, empires 1, cx prefs 1 on his account). Still unknown: the OpenAPI spec at https://doc.fnar.net/api.json has no securitySchemes. Probe with read-only calls.
 - (resolved) PRUNplanner `exchanges/` has vwap_daily/7d/30d and traded volume; merged into `puga/market.py`. Trend history via cxpc still todo.
 - Extraction: concentration to daily rate formula.
+- (resolved 2026-09-25) Real price-band filtering (`NarrowPriceBandLow/High`, `WidePriceBandLow/High`) implemented in `puga/saturation.py` (`in_band`, `effective_demand`, `effective_supply` band param) and wired into `tools/scan.py` stage 2. Was flagged as an unimplemented refinement in saturation-design.md since day one; the player noticed a stale out-of-band bid in a live screenshot and asked the right question.