Simulator backend

Internal kernel only — no external reservoir-sim bridge (ECLIPSE / tNavigator / INTERSECT / CMG). All physics live in `src/lib/planar3d/*` and `src/lib/depletion*`; the on-screen 'Coupled wellbore + reservoir run' label refers to the in-house sandbox, not a third-party solver front-end. **Phase 17 — one-way static-LGR fracture-geometry export** via `src/lib/reservoir/fractureLgrExport.ts` (`buildFractureLgrExport`): takes any `SurfaceMesh` (post-pump, post-weld, multi-stage snapshot) + a coarse host-grid spec (`nx/ny/nz`, `dxFt/dyFt/dzFt`, origin) and emits a vendor-neutral CSV (`stage, face_id, host_i/j/k, lgr_i/j/k, cx/cy/cz_ft, dx/dy/dz_ft, perm_md, porosity, opening_in, area_ft2`) ready for CARFIN (ECLIPSE), LGR (tNavigator) or REFINE (CMG) after light receiving-side adapter scripting. Uniform per-host-cell refinement (default 4×4×1), out-of-bounds clamp w/ manifest count, cubic-law parallel-plate permeability fallback (`k_mD = (w_in·0.0254)²/12 · 1.013e15`) when no `permMdAt` callback is supplied, byte-stable when `nowIso` is fixed. ONE-WAY ONLY — geometry handoff; the external simulator owns the production solve. Drift-guard: `fractureLgrExport.test.ts` (9 tests — banner+header lock, manifest fields, LGR cell sizing, host (i,j,k) attribution, clamp counting, cubic-law fallback, callback overrides, input validation, byte-stability).

Phase 17 promotion CLOSED — one-way static-LGR / RESCUE-style fracture-geometry export shipped as pure CSV builder. Out of scope: two-way handshake with ECLIPSE / tNavigator / INTERSECT / CMG (the external simulator owns the production solve). Ergonomics SHIPPED — the exporter is now a first-class button on `ReservoirExportPanel` (`Export fracture LGR (.csv)`) alongside GRDECL / RESQML / Petrel-handoff, emitting the per-face CSV plus a JSON manifest and defaulting the host coarse grid to the resolved ReservoirState extents centred on the mesh; the button self-disables with an explanatory tooltip until a non-planar surface mesh is present. Next up: feed it directly from the per-simulation Results-tab `NonPlanar3DResultsCard` mesh state so multi-stage snapshots export without re-running.

• Two-way handshake with ECLIPSE / tNavigator / INTERSECT / CMG

1. Phase 17

   shipped

   , not a third-party solver front-end. **Phase 17 — one-way static-LGR fracture-geometry export** via `src/lib/reservoir/fractureLgrExport.ts` (`buildFractureLgrExport`): takes any `SurfaceMesh` (post-pump, post-weld, multi-stage snapshot) …

2. Phase 17

   planned

   Phase 17 promotion CLOSED — one-way static-LGR / RESCUE-style fracture-geometry export shipped as pure CSV builder. Out of scope: two-way handshake with ECLIPSE / tNavigator / INTERSECT / CMG (the external si