spacecost 0.3.0

Data contract pipeline_version unchanged at 1.15.0, and that is the
headline rather than a footnote: build_catalog() writes the same seven CSVs
byte for byte, reference/ needed no regeneration, and economicspace does
not have to re-run Stage 3 for this. A repin is enough. The rule is
one-directional and this release is the other direction: new code, no new data.

A seventh module: delivery, the staged leg chains

Moved out of economicspace's modules/mineral_value.py (Stage 2), where it had
lived since that module's v1.2.0. It answers two questions:

• delivered_cost_usd_per_kg(dest) — the launch cost a kilogram already in
  space avoids, walked backwards through a chain of real stages.
• downleg_cost_usd_per_kg(dest) — capsule, TPS, a share of the recovery
  campaign, and the departure burn that has to carry all three.

plus delivery_mass_ratio and stage_mass_ratio, and the constants behind
them: DELIVERY_CHAINS, DOWNLEG_DEPARTURE_DV_M_S, LEO_LAUNCH_USD_PER_KG,
MARS_LANDED_MASS_FRACTION.

Why here. The block it came from opened by admitting what it was: "Constants
below are cross-referenced to Module 3. They are duplicated rather than
imported because Module 2 runs BEFORE Module 3 in the pipeline order … If you
change one of these, change it in Module 3 too." Nine numbers retyped by hand
under a manual-sync instruction. That justification was concatenation order,
and it stopped applying the moment Stage 3 became this package: a pip-installed
package has no position in a pipeline. Nothing in the block knows what an
asteroid is.

Every chain delta-v is now a lookup, not a literal. DELTA_V_REFERENCE is
the single authority for all nine, and tests/test_delivery.py fails if a
literal creeps back in.

⚠️ The downleg delta-v are typed, and that is deliberate. Four of six
agree with a row exactly; a LEO deorbit burn has no row at all, and the GEO
figure disagrees with GEO -> Earth (deorbit to entry) by 2 m/s. Deriving all
six uniformly would have moved two published prices under a release that claims
to move none. They stay as literals with the mismatch tabulated beside them.
Reconciling those two is a real question and a separate release, because it
changes what a kilogram of platinum is worth at GEO and in LEO.

⚠️ math.exp, not np.exp. rocket.py is the vectorised entry point and
this is the scalar one, and they are not interchangeable: the consumer argues
its releases from bit-identity and the two libraries may round the last bit
differently. Do not unify them.

Pinned bit-exact. tests/test_delivery.py holds all fourteen headline
values to full repr precision, captured by running the original
implementation before a line was edited — not a regression net taken
afterwards. An exact ==, because a tolerance would defeat the purpose.
Proved able to fail by perturbing the arithmetic, typing a literal into a chain,
and collapsing the None/[] distinction.

⚠️ CONSUMER SURFACE WIDENED, and it is a new shape. Four names joined
tests/test_consumer_contract.py, and they are imported by economicspace's
Stage 2, not its Stage 3 adapter. Stage 2 is the first stage to reach this
package, so a name dropped here now fails a pricing stage that runs before the
adapter does, and the traceback will not mention Stage 3.

⚠️ REPIN economicspace, in the FIVE places it now types the tag:
requirements.txt, _MASTER_PIP_SPEC in build_master.py, _PIP_SPEC in
modules/transportation.py, the same in modules/mineral_value.py (new with
this release), and the README sentence naming it.