Add structural calculation worksheets

Collection of engineering calculation projects (Python + Typst), each with
input, calc script, tests, results, and generated PDF where available.

slab-on-grade/slab-on-grade.typ

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+#import "assets/sheet.typ": calcline, calcsheet, check
+
+#show: calcsheet.with(
+  title: "Slab-On-Grade Design",
+  project: "Pinecrest Residence",
+  prepared-by: "Conemco Engineering",
+)
+
+#let round(value, digits: 2) = calc.round(value, digits: digits)
+
+= Slab-On-Grade Design
+
+Considering 4" thick, 3000 psi slab on grade with 6x6 w.2.1. For interior use.
+
+== Input Data
+
+#let t = 5
+#let L = 15
+#let fc = 3000
+#let wc = 150
+#let fy = 60000
+#let fs = (2 / 3) * fy
+#let DL = 20
+#let LL = 100
+#let b = 12
+
+#calcline([$t = #t " in"$], [Slab thickness])
+#calcline([$L = #L " ft"$], [Max joint spacing])
+#calcline([$f'c = #fc " psi"$], [Concrete strength])
+#calcline([$omega_c = #wc " pcf"$], [Concrete density])
+#calcline([$f_y = #fy " psi"$], [Steel strength])
+#calcline([$f_s = (2\/3) f_y = #fs " psi"$], [Working stress])
+#calcline([$D_L = #DL " psf"$], [Dead load])
+#calcline([$L_L = #LL " psf"$], [Live load])
+#calcline([$b = #b " in"$], [Design width])
+
+== Acting Load
+
+#let w = wc * (t / 12) + DL + LL
+
+#calcline(
+  [$w = omega_c dot t + D_L + L_L = #round(w) " psf"$],
+  [Design lineal load],
+)
+
+== Required Steel Reinforcement
+
+#let F = 1.5
+#let As_req = (F * L * w) / (2 * fs)
+
+#calcline([$F = #F$], [Subgrade friction factor])
+#calcline(
+  [$A_(s,"req") = display((F L w) / (2 f_s)) = #round(As_req, digits: 4) " in²/ft"$],
+  [Required steel reinf area using subgrade drag equation],
+)
+
+== Provided Steel Reinforcement
+
+#let As = 0.058
+
+#calcline(
+  [$A_s = #As " in²/ft"$],
+  [Provided steel reinf. area #linebreak() WWF 6"x6" 2.9x2.9],
+)
+
+#v(8pt)
+#check(
+  "Provided steel reinforcement",
+  As_req,
+  As,
+  unit: "in²/ft",
+  demand-label: [$A_(s,"req")$],
+  capacity-label: [$A_s$],
+)