Turn the single boat into a fleet with dedicated roles

[dmccoystephenson]

Summary

One boat that could only fish becomes any number of boats, each dedicated to a role. Two new modules carry it:

• src/business/boats.py — the fleet, the four roles, and crew assignment.
• src/business/voyages.py — the job boards for the three active roles.

Role	What she does
Fishing	Crew bring in a catch every morning. The only role that catches anything.
Hauling	Freight contracts, and half again the export capacity of the same hull in any other role.
Piracy	Raids. Pays far better than honest work, and can cost a crew member permanently.
Transport	Passenger runs: less money, but guaranteed and never damages the boat.

Crew come from one shared roster. A new hire goes aboard the first boat with a free berth and can be moved between boats afterwards. Wages are owed on every hand hired whether or not they have a berth, so an idle boat is a real cost — and when payroll can't be met, the idle hands quit first. Only crew on a fishing boat bring in a catch, so where people stand is now a decision with a number attached.

Voyages cost a day, same as an export run. Pay scales with hull tier and crew size.

Piracy is the deep one, and shows its real odds before the player commits — a full-crewed Fishing Fleet is ~90% against the Saltmarsh skiffs but 47% (with a 16% disaster risk) against the escorted Thornhaven bullion run. Four outcomes: a rich take, an ordinary take (plus fish seized off their hold, straight into yours), driven off with a scratched hull, or a disaster that takes a villager the player hired by name off the boat and off the roster for good. Damage is lasting — past halfway a boat can't sail until the yard is paid.

Compatibility

player.hasBoat and player.boatTier are now read-only properties derived from the fleet, so the flag and the tier can't disagree any more (they previously could). Every read site is unchanged; write sites went through boats.addBoat.

A save written before roles existed has no boats key, so it's migrated into a single fishing boat carrying the whole crew — the exact meaning that save had. Nobody loses a boat or a hand by loading an old file, and hasBoat/boatTier are still written out so an older build can read a modern save. There are live save slots on the production box, so this path has its own tests.

business.py is now just the tier catalogue; production, crew and selling moved to boats.py, which lets boats.py depend on it without an import cycle. tests/business/test_business.py was split accordingly, with the fleet half becoming tests/business/test_boats.py.

Test plan

• python3 -m compileall -q src tests
• SDL_VIDEODRIVER=dummy SDL_AUDIODRIVER=dummy python3 -m pytest --verbose -vv --cov=src --cov-report=term-missing --cov-report=xml:cov.xml — 594 passed, 97% total. voyages.py 100%, player.py 100%, playerJsonReaderWriter.py 100%, boats.py 96%, docks.py 93% (remaining gaps are pre-existing fish() branches).
• black + autoflake over the changed files only.
• Front-end parity. Everything new goes through showOptions/showInteractiveDialogue/currentPrompt — no new primitive, so console, pygame and web all get it.
• Played it through the real console front-end: built a three-boat fleet, moved crew between boats, read the raid odds off the job board, ran a successful raid (took $1,908 and 12 fish), and forced a disaster to check it reads right and actually removes the villager.
• The docks-menu tests now drive menus by label rather than position (fleetChooser), so adding an option no longer breaks a dozen unrelated tests.

Balance note

A raid on the top target beats a hauling contract on the same hull by a wide margin, which is the point — but it's gated behind a tier-3 boat, a real crew, and a 16% chance of losing one of them plus a repair bill. Happy to tune the loot bands or the disaster share if it plays too hot.