ui/phase-18: ship-class calc bridge with live designer preview

Wires pkg/calc/ship.go into the WASM Core boundary as seven thin
wrappers (DriveEffective, EmptyMass, WeaponsBlockMass, FullMass,
Speed, CargoCapacity, CarryingMass). The ship-class designer reads
Core through a new CORE_CONTEXT_KEY populated by the in-game layout
and renders a five-row preview pane (mass, full-load mass, max
speed, range at full load, cargo capacity) that updates reactively
on every form edit and on the player's localPlayer{Drive,Weapons,
Shields,Cargo} tech levels — three of which are now decoded from
the report's Player block alongside the existing localPlayerDrive.

CarryingMass is the seventh wrapper added to the original six-function
list so that "full-load mass" composes through pkg/calc/ functions
without putting math in TypeScript.

ui/PLAN.md

@@ -2012,28 +2012,44 @@ Targeted tests:
   class, list it, delete it; rejected-submit kept; field-validation
   kept (Save disabled with localised tooltip).
 
-## Phase 18. Ship Classes — Calc Bridge
+## ~~Phase 18. Ship Classes — Calc Bridge~~
 
-Status: pending.
+Status: done.
 
 Goal: wire `pkg/calc/` ship math into the designer for live mass,
 speed, range, and cargo capacity previews.
 
 Artifacts:
 
-- `ui/core/calc/ship.go` thin Go bridge wrapping `pkg/calc/.FullMass`,
-  `EmptyMass`, `Speed`, `CargoCapacity`, `WeaponsBlockMass`,
-  `DriveEffective` in JSON-marshallable signatures, exported through
-  the `Core` API
-- `ui/frontend/src/platform/core/index.ts` extends `Core` interface
-  with the new calc methods
-- live-updating preview pane in the ship-class designer showing mass,
-  full-load mass, max speed, range, and cargo capacity at the player's
-  current tech levels
-- audit step recorded in `ui/docs/calc-bridge.md`: every wired
-  function listed against its `pkg/calc/` source
-- if any required `pkg/calc/` function is missing, this phase raises a
-  blocker and the function is added to `pkg/calc/` first (owner-led)
+- `ui/core/calc/ship.go` thin Go bridge wrapping seven functions
+  from `pkg/calc/ship.go` — `DriveEffective`, `EmptyMass`,
+  `WeaponsBlockMass`, `FullMass`, `Speed`, `CargoCapacity`,
+  `CarryingMass` — each as a one-line passthrough; the seventh
+  function (`CarryingMass`) was added during stage implementation
+  to let the preview compose `full-load mass` from `CargoCapacity`
+  without injecting math into TS;
+- `ui/wasm/main.go` registers the seven wrappers under
+  `globalThis.galaxyCore`; `ui/frontend/src/platform/core/index.ts`
+  extends `Core` with the matching typed methods (`emptyMass` and
+  `weaponsBlockMass` return `number | null`, mirroring the Go
+  `(_, false)` validator path);
+- `ui/frontend/src/api/game-state.ts` extends `GameReport` with
+  `localPlayerWeapons`, `localPlayerShields`, `localPlayerCargo`
+  alongside the existing `localPlayerDrive`. The decoder reads
+  all four from the `Player` row in the report's player block.
+  Phases 19-21 reuse these fields without re-extending the report;
+- `ui/frontend/src/lib/core-context.svelte.ts` exposes a
+  `CoreHolder` through `CORE_CONTEXT_KEY`. The in-game layout
+  (`routes/games/[id]/+layout.svelte`) populates the holder after
+  `loadCore()` resolves, so the designer reads `Core` from context
+  without re-booting WASM;
+- live-updating preview pane in the ship-class designer showing
+  empty mass, full-load mass, max speed (at empty), range at full
+  load, and cargo capacity per ship at the player's current tech
+  levels; the pane only renders when the form passes validation
+  *and* `Core` is ready;
+- audit step recorded in `ui/docs/calc-bridge.md`: live surface
+  table lists every wired function against its `pkg/calc/` source.
 
 Dependencies: Phases 5 (Core skeleton), 17.
 
@@ -2047,11 +2063,14 @@ Acceptance criteria:
 
 Targeted tests:
 
-- Go parity tests in `ui/core/calc/` against `pkg/calc/` outputs on
-  shared fixtures;
-- Vitest snapshot tests for the preview pane on canonical inputs;
-- Playwright e2e: edit a ship class, observe preview updates and
-  submit, confirm server-side mass matches.
+- Go parity tests in `ui/core/calc/ship_test.go` against `pkg/calc/`
+  outputs on shared fixtures, plus a composition test that exercises
+  the exact preview pipeline (empty → cargo capacity → carrying mass
+  → full-load mass → speed at empty + at full);
+- Vitest coverage in `ui/frontend/tests/designer-ship-class.test.ts`
+  asserts preview hidden until validation passes, hidden when no
+  `Core` is available, renders five rows with computed values once
+  the form is valid, and reactively refreshes on subsequent edits.
 
 ## Phase 19. Inspector — Ship Group (Read-Only)
 
@@ -2112,7 +2131,9 @@ Artifacts:
   `SendGroup`, `LoadCargo`, `UnloadCargo`, `Modernize`, `Dismantle`,
   `TransferToRace`, `AssignToFleet` command variants
 - `Send` action picks destination through a planet picker filtered by
-  the group's reach (uses `pkg/calc/` reach function via Core)
+  the group's reach (uses `pkg/calc/` reach function via Core; the
+  player's tech levels are already on `GameReport.localPlayer*` from
+  Phase 18, no extra plumbing needed)
 - `Modernize` cost preview using `pkg/calc/` formula via Core
 - confirmation dialog for `Dismantle` over a foreign planet with
   colonists onboard (special-case from [`rules.txt`](../game/rules.txt): colonists die)