Inline N alongside kg + spell out Safety factor on spec card

BACKLOG.md

@@ -68,7 +68,7 @@ If any seat would be confused, the component fails.
 ### Spec detail (`/problems/:roundId/:specId`)
 
 - Spec header + plain-English summary — ● ● ● — sentence above diagram ties material+load+arm+MPa together; chips on H1 row carry tooltips. (step 344, `735dbec`)
-- Spec spec-card (material / load / wall / overhang / score) — ◐ ◐ ○ — units (N vs kg) repeated; "SF 1.5×" cryptic.
+- Spec spec-card (material / load / wall / overhang / score) — ● ● ● — Load chip now reads `15 kg (149 N) load` with cross-unit inline (was `15 kg load`); chip tooltip explains "149 N is the force the FEA solver applies; 15 kg is the everyday equivalent" so a first-timer reading the chip AND the SpecDiagram's `↓ 149N` label sees the units agree instead of wondering "wait, is it 15 or 149?". `SF 1.5×` → `Safety factor 1.5×` per step 280 spell-out pattern (no abbreviations on first-contact UI); tooltip now resolves the multiplier to the concrete `27 MPa` allowable for this material. Plain-English paragraph also gains `(149 N)` after `15 kg` so the cross-unit reads identically in prose. (`HeroStats.tsx` L168-182, L203-209, step 381)
 - `SpecDiagram` (front view + side view miniature) — ○ ○ ○ — too small; load arrow direction not labeled.
 - 4 KPI tiles (best mass / vs reference / stress margin / passing entries) — ● ● ● — clean.
 - "Maintainer reference still leads" banner — ● ● ● — banner now front-loads the category direction sentence ("Lower mass wins this category" / "Higher stiffness wins this category" / "Lower deflection wins this category") before the gap %, and uses metric-specific gap verbs ("is 5.2% heavier than the reference at 263.20 g" / "still falls X% short of the reference at Y N/(mm·g)" / "deflects X% more than the reference at Y mm"). Bar-to-beat is inline with the percentage so a first-timer reads direction → gap → concrete target in one pass. (`HeroStats.tsx` L281–319, step 352)

src/components/HeroStats.tsx

@@ -166,14 +166,14 @@ export function HeroStats({ spec, sota, submissionCount, round }: Props) {
             {MATERIAL_META[spec.material]?.label ?? spec.material.toUpperCase().replace(/_/g, " ")}
           </InfoChip>
           <InfoChip
-            title={`${spec.constraints.load_newtons.toFixed(0)} N (≈ ${loadKg} kg under Earth gravity) applied downward (-Z) at the arm tip — the load point. Your design must survive this without exceeding the allowable stress.`}
+            title={`${spec.constraints.load_newtons.toFixed(0)} N is the force the FEA solver applies; ${loadKg} kg is the everyday equivalent (1 kg ≈ 9.81 N under Earth gravity). The load points downward (-Z) at the arm tip. The diagram below shows the same number in newtons — the units match, only the framing differs.`}
           >
-            {loadKg} kg load
+            {loadKg} kg <span className="text-forge-muted/70">({spec.constraints.load_newtons.toFixed(0)} N)</span> load
           </InfoChip>
           <InfoChip
-            title={`Safety factor ${spec.constraints.safety_factor}× — yield stress ÷ SF = max allowable stress. Higher = stricter design requirement.`}
+            title={`Safety factor ${spec.constraints.safety_factor}× — yield stress ÷ safety factor = max allowable stress (${allowable.toFixed(0)} MPa for this material). Higher safety factor = stricter design requirement.`}
           >
-            SF {spec.constraints.safety_factor}×
+            Safety factor {spec.constraints.safety_factor}×
           </InfoChip>
           <InfoChip
             title={`Max allowable stress = ${spec.material.includes("aluminum") || spec.material.includes("stainless") ? "yield strength" : "tensile strength"} ÷ safety factor ${spec.constraints.safety_factor}×. Your design's peak von Mises stress must stay below this. MPa = megapascals (unit of pressure/stress).`}
@@ -201,7 +201,8 @@ export function HeroStats({ spec, sota, submissionCount, round }: Props) {
         <p className="text-forge-text/85 text-xs leading-relaxed max-w-2xl mb-4">
           <span className="text-white font-semibold">In plain English:</span>{" "}
           a <span className="text-white">{materialLabel}</span> bracket bolted to a wall must hold{" "}
-          <span className="text-white">{loadKg} kg</span> pulling{" "}
+          <span className="text-white">{loadKg} kg</span>{" "}
+          <span className="text-forge-muted">({spec.constraints.load_newtons.toFixed(0)} N)</span> pulling{" "}
           <span className="text-white">straight down</span> at the tip of a{" "}
           <span className="text-white">{armMm} mm</span> cantilever arm, without exceeding{" "}
           <span className="text-white">{allowable.toFixed(0)} MPa</span> peak stress (safety factor{" "}