feat(ui): Phase 30 ship-class calculator with goal-seek and reach circles

Fuse the standalone ship-class designer (Phases 17/18) into a sidebar calculator: live mass/speed/attack/defence/bombing results, a planet build-rate readout, single-target goal-seek, a modernization-cost mode, and auto reach circles on the map for the selected planet.

pkg/calc becomes the single source for the new math (no mirroring): extract BombingPower from the engine model and the per-turn ship-production loop from controller.ProduceShip into pkg/calc (engine now delegates), and add inverse goal-seek solvers in pkg/calc/solve.go. Thin-bridge the combat, planet-build, and solver functions through ui/core/calc + ui/wasm and rebuild core.wasm.

Remove the standalone designer view/route; the ship-classes table and the view/bottom menus open the calculator via a shared request store.

Docs: rewrite ui/PLAN.md Phase 30, adjust Phase 34 (realistic forecast + CAP/COL ownership), add ui/docs/calculator-ux.md, extend calc-bridge.md, fix navigation.md; remove ui/CALCULATOR.md.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/docs/calculator-ux.md

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+# Ship Class Calculator — UX
+
+Phase 30 fuses the ship-class designer and a calculator into one sidebar
+tool (`lib/sidebar/calculator-tab.svelte`). It replaced the standalone
+designer view/route from Phases 17/18. All numeric math lives in
+`pkg/calc` and is reached through the `Core` WASM bridge; the calculator
+holds input state and orchestrates, it never computes.
+
+## Modes
+
+- **Calculator** (`ship`): the full tool — design area, derived results,
+  planet build, goal-seek.
+- **Modernization**: reuses the design area and shows per-block and
+  total `BlockUpgradeCost` from the current tech to an editable target
+  tech. The design-area component is extracted
+  (`lib/calculator/ship-design-area.svelte`) so the future ship-group
+  upgrade flow can reuse it.
+
+The `path` mode from the original plan was dropped (MVP path-finding is
+brute force); reach circles on the map replace it. `bombing` is folded
+in as a per-ship result rather than a separate mode.
+
+## Areas
+
+1. **Ship Class design area** — five blocks (drive, armament, weapons,
+   shields, cargo) and four tech levels (drive, weapons, shields,
+   cargo). Tech defaults to the player's current tech and shows a lock
+   icon once overridden; clicking it resets to the default.
+2. **Calculator area** — derived results: empty/loaded mass, empty/
+   loaded speed, attack, defence, bombing (per ship), cargo capacity.
+   A load toggle (empty / full / custom) sets the cargo load that the
+   loaded-column results use.
+3. **Planet area** — when an own planet is selected on the map, shows
+   its MAT (overridable) and the single-turn build rate (ships per turn,
+   turns per ship). The realistic multi-turn forecast with CAP/COL
+   supply is Phase 34.
+
+## Locks and goal-seek
+
+Two distinct lock semantics share one icon (a closed padlock; it only
+appears once a value is pinned, click to release):
+
+- **Override locks** on inputs that have a default — the four techs and
+  the planet MAT. Editing one overrides the default; the lock resets it.
+  Any number may be overridden at once.
+- **Goal-seek locks** on derived results. Pinning a result back-solves
+  the single input it claims, which then renders read-only (computed):
+
+  | result        | claims        |
+  | ------------- | ------------- |
+  | attack        | weapons block |
+  | defence       | shields block |
+  | empty speed   | drive block   |
+  | loaded speed  | drive block   |
+  | empty mass    | cargo block   |
+  | loaded mass   | cargo load    |
+
+  Only **one** result may be locked at a time (the others' lock
+  affordances disable with a tooltip). An unreachable target — e.g. a
+  speed at or above the stripped-hull ceiling `20 × driveTech`, or a
+  solved block that fails the value rules — leaves the locked cell in a
+  red error state and does not apply. Inverse solving lives in
+  `pkg/calc/solve.go`; the bisection for defence → shields is the only
+  non-analytic case.
+
+## Create / load / delete
+
+The name field is a combobox over the player's existing classes. Picking
+an existing class loads it as a template (so you can tweak and Create a
+new one); Create is disabled while the name is invalid or duplicate
+(reusing `lib/util/ship-class-validation.ts`). When a saved class is
+loaded, a Delete affordance appears. Create / Delete reuse the existing
+`createShipClass` / `removeShipClass` order-draft flow, so the optimistic
+overlay reflects the change immediately. Ship classes are immutable after
+creation (per `game/rules.txt`), so there is no edit — only Create-new
+and Delete.
+
+## Reach circles
+
+When an own planet is selected in calculator mode, the calculator
+publishes the planet origin and the design's loaded speed to a shared
+store (`lib/calculator/reach.svelte`). The map view
+(`lib/active-view/map.svelte`) reads it and draws 1–3 thin concentric
+reach circles (`map/reach-circles.ts`) for 1/2/3 turns. The ring count
+shrinks as speed grows: a ring is dropped once the previous one reaches
+the torus wrap-midpoint (half the shorter side) or the no-wrap map edge
+(farthest corner). The circles clear when the selection clears or the
+design is invalid.
+
+## State preservation and history
+
+Calculator inputs are component-local state. The sidebar keeps the tab
+mounted while the player navigates between active views, so inputs
+persist across view switches per the global state-preservation rule
+(`ui/docs/navigation.md`). Tech levels track the rendered report, so in
+history mode the calculator computes against the viewed snapshot's tech.
+
+The ship-classes table and the view/bottom menus open the calculator via
+a shared request store (`lib/calculator/load-request.svelte`): the
+in-game layout flips the sidebar to the calculator tab and the
+calculator loads the requested class (or starts a fresh design).
+
+## Layout and mobile
+
+Everything stacks vertically to fit the 18 rem sidebar; the design and
+result rows use compact two-column (ship/tech, empty/loaded) grids. On
+mobile the sidebar is the existing bottom-sheet/overlay; the calc bottom
+tab opens it.
+
+## Runtime note
+
+The new bridge functions are only present after `make wasm` rebuilds
+`ui/frontend/static/core.wasm` (needs TinyGo). Vitest injects a fake
+`Core` (`tests/fake-core.ts`) mirroring `pkg/calc`, so unit/component
+tests do not need the rebuild; the Playwright suite and the live app do.