Docs: register shipping/lmscan tools, gateway mechanics findings

CLAUDE.md/docs/roadmap.md/docs/library.md: register tools/shiptrip.py,
tools/shipcost.py, tools/lmscan.py, and puga/shipping.py/puga/contracts.py
per this project's usual pattern of recording new tools where every other
tool is listed.

docs/mechanics.md: new "Gateway (GTW) jump transit time" section - our own
measured GTW segment durations scale ~linearly with parsec distance
(~20 min/parsec across 3 distinct distances), contradicting a 2024
pre-launch forum comment about a possibly-fixed transit time. Also notes
the handbook-confirmed facts not modelled anywhere yet: one-way gateway
links and per-gateway max jump volume.

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

docs/library.md

@@ -49,6 +49,23 @@ EOF
   -> SystemId), `shortest_path(src, dst, graph=None)` (Dijkstra by straight-line ly over FIO's
   `/systemstars` jump graph; returns jumps, distance_ly, path). Not a PRUNplanner feature, built
   for this project since travel isn't modelled anywhere else. CLI: `tools/route.py`.
+- **`puga.shipping`** — `cruise_leg_fuel(v0)`, `jump_fuel(v1)`, `charge_fuel(v1)`,
+  `gateway_hop_cost(lock_fee_amount, lock_fee_currency)`, `landing_fuel(planet_natural_id)` (lookup
+  only, `None` if unmeasured), `trip_fuel(...)` (one-way total, shared by the CLIs),
+  `leg_cost(src, dst, sf_price, ff_price, v0=1.0, v1=1.0)` (one-way AIC cost; uses
+  `KNOWN_GATEWAY_ROUTES` when the pair has a measured gateway chain, else the direct-jump graph;
+  `None` if neither applies), `round_trip_cost(...)` (there-and-back via two `leg_cost` calls,
+  `None` if either leg is unpriceable or carries a non-AIC fee - used by `tools/network.py`'s
+  freight cost): real ship flight fuel model, linear in the fuel-usage (v0) / reactor-usage (v1)
+  sliders, additive/no cross-term. Scoped to this account's one hull/reactor (BP-STRT-0000, both
+  ships confirmed identical); see the module
+  docstring for confirmed-vs-open caveats before trusting a number. CLIs: `tools/shiptrip.py`
+  (ship+from+to, auto-computes everything via `puga.route`), `tools/shipcost.py` (explicit
+  jumps/sliders/gateway-fees, for when you already know the breakdown). Raw calibration data:
+  `empire/data/shipping_calibration/`.
+- **`puga.contracts`** — `scan(planet, direction, sf_price, ff_price, v0=1.0, v1=1.0)`: live
+  Local Market hauling ads (FIO `/localmarket/shipping/{source,destination}`), each enriched with
+  real one-way fuel cost (`puga.shipping.leg_cost`) and margin. CLI: `tools/lmscan.py`.
 - **`puga.undervalued`** — `manufacturing_candidates()`, `current_margin(ticker, recipe, cx)`,
   `scan_current(cx, min_vol=5.0)`: manufactured goods priced below implied production cost, for
   a buy-and-hold-for-reversion trade, not a build decision. Backtested expected return is