Add eve-fit-engine to community resources

docs/community/eve-fit-engine/index.md

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+---
+search:
+  exclude: true
+
+title: eve-fit-engine
+type: resource
+description: Pyfa-parity ship and Upwell-structure fitting calculation engine for JavaScript. Give it a fit, get the full derived stat block.
+maintainer:
+  name: TremalJack
+  github: WilliamFalci
+---
+
+# eve-fit-engine
+
+`eve-fit-engine` is an npm package that computes the derived stat block of an EVE Online
+ship or Upwell structure fit: offense (DPS, alpha, application), defense (EHP, resists,
+active and passive tank), capacitor (stability and simulation), navigation, targeting,
+fitting (CPU / powergrid / calibration), projected effects, and structure fuel and
+service stats.
+
+It is the calculation engine behind [Capsuleers.app](https://capsuleers.app), extracted
+so that other developers can build fitting tools without reimplementing dogma.
+
+<div class="grid cards" markdown>
+
+- [:octicons-mark-github-16: __GitHub__](https://github.com/WilliamFalci/capsuleers.fitting-engine){ .esi-card-link }
+- [:simple-npm: __npm__](https://www.npmjs.com/package/eve-fit-engine){ .esi-card-link }
+- [:simple-discord: __Discord__](https://discord.com/invite/hdbtSFBGD3){ .esi-card-link }
+
+</div>
+
+## Two entry points
+
+- **Base (`eve-fit-engine`)** — framework-free. No `fetch`, no `fs`, no `window`, no npm
+  runtime dependencies. You inject your own `FittingDataset`, so it runs in the browser,
+  in Node, or in a worker, against whichever SDE snapshot you keep.
+- **Node (`eve-fit-engine/node`)** — batteries included. Ships a version-pinned snapshot of
+  the EVE Static Data Export plus a loader, so an EFT string in gives full stats out with
+  nothing else to set up.
+
+```ts
+import { computeFromEft } from 'eve-fit-engine/node'
+
+const { computed } = await computeFromEft(`
+[Rifter, My Fit]
+200mm AutoCannon II, Republic Fleet EMP S
+200mm AutoCannon II, Republic Fleet EMP S
+1MN Afterburner II
+Gyrostabilizer II
+`)
+
+computed.derived.offense.totalDps
+computed.derived.defense.ehpTotalAgainstProfile
+computed.derived.navigation.maxVelocity
+```
+
+Skills default to all-V; pass a `skillProfile`, `damageProfile` or `targetProfile` to
+override.
+
+## Correctness
+
+The engine is validated against [Pyfa](https://github.com/pyfa-org/Pyfa) two ways, because
+a fitting engine that is *nearly* right is a fitting engine nobody can trust:
+
+- **Fixture suite** — 662 hand-curated assertions against Pyfa, all-V skills, zero
+  tolerance. This is the release gate.
+- **Differential harness** — generates four fits for *every* published ship and compares
+  every stat against a headless Pyfa oracle. **1662 of 1676 fits (99.2%) match exactly**;
+  the residual is a documented set of Pyfa float and per-ship modelling quirks, listed in
+  the repository rather than hidden.
+
+## Licensing
+
+The engine is **GPL-3.0-or-later**: it is a derivative work of Pyfa, whose calculation
+semantics it mirrors, and it is distributed under the same terms. The complete
+corresponding source is the linked repository.
+
+The bundled SDE snapshot is included by mere aggregation and is **not** covered by the
+GPL — it remains governed by the EVE Online Developer License Agreement. See `NOTICE` and
+`data/SDE-LICENSE.md` in the repository.