feat: gate heavy solver JSON, field traceability API, GUI rod/export depth

- C: emit profiles/diagnostics/fourier only when enable flags are set; null otherwise
- API: fieldTraceability on case parse/default and solve; fix GET /solve/default options
- Tests: golden fingerprint, quality gates, C diagnostics invariants; cardQa mean empty guard
- Makefile: test-solver-sanitize ASan/UBSan target; README and COMPUTE_PLAN updates
- GUI: taper weight/MTS/guides/sinker round-trip, rod catalog, solver output toggles,
  results (profiles/diagnostics/Fourier/traceability), engineering checks and tabs
- Restore canonical WellName in base-case for regression; trace TaperGuidesCountArray

Made-with: Cursor

gui-ts/src/ui/tabs/PumpTab.tsx

@@ -1,26 +1,50 @@
+import { useMemo } from "react";
 import type { CaseStore } from "../../state/useCaseStore";
 import { Fieldset } from "../common/Fieldset";
 import { Row } from "../common/Row";
 import { NumberField } from "../common/NumberField";
 import { SelectField } from "../common/SelectField";
+import {
+  PUMP_PLUNGER_INCH_OPTIONS,
+  formatPumpDiameterDual,
+  pumpDiameterMmFromInches
+} from "../../state/unitsDisplay";
 
 type Props = { store: CaseStore };
 
 export function PumpTab({ store }: Props) {
   const { state, update } = store;
+
+  const pumpOptions = useMemo(() => {
+    const mmVals = PUMP_PLUNGER_INCH_OPTIONS.map((inchVal) => pumpDiameterMmFromInches(inchVal));
+    const opts = PUMP_PLUNGER_INCH_OPTIONS.map((inchVal, i) => ({
+      value: mmVals[i],
+      label: formatPumpDiameterDual(mmVals[i], state.unitsSelection)
+    }));
+    const known = opts.some((o) => Math.abs(o.value - state.pumpDiameter) < 0.001);
+    if (!known && state.pumpDiameter > 0) {
+      opts.unshift({
+        value: state.pumpDiameter,
+        label: formatPumpDiameterDual(state.pumpDiameter, state.unitsSelection)
+      });
+    }
+    return opts;
+  }, [state.pumpDiameter, state.unitsSelection]);
+
   return (
     <div className="tab-grid two">
       <Fieldset legend="Pump Geometry">
         <Row
-          label="Plunger Diameter"
+          label="Plunger diameter"
           htmlFor="plungerDiam"
-          hint="mm in base-case XML (converted to m if > 2)"
+          hint="Stored as mm in the case file when above 2 (same convention as rod OD)."
         >
-          <NumberField
+          <SelectField
             id="plungerDiam"
             value={state.pumpDiameter}
-            step={0.25}
+            options={pumpOptions}
             onChange={(v) => update("pumpDiameter", v)}
+            ariaLabel="Pump plunger diameter"
           />
         </Row>
         <Row label="Pump Friction" htmlFor="pumpFric" hint="lbf (imperial)">