Add structural calculation worksheets

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

wood-joist/README.md

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+# Worksheets
+
+Typst-first calculation sheets. Use Python only when the arithmetic is no longer comfortable in Typst.
+
+```text
+lib/sheet.typ                 Shared letterhead, calc-line, check, check_service
+calcs/shore-post/             Typst-only completed calculation
+calcs/concrete-beam/          YAML numbers → Python → JSON → Typst
+calcs/concrete-beam2/         YAML quantities → Pint → JSON → Typst
+calcs/steel-beam/             YAML quantities → Pint + AISC XLSX → JSON → Typst
+calcs/wood-joist/            YAML quantities → Pint → JSON → Typst (NDS 2018 ASD)
+calcs/concentric-footing/    YAML quantities → Pint → JSON → Typst (ACI 318-19)
+```
+
+Compile every sheet from this folder so the shared logo resolves.
+
+## Typst-only
+
+Edit numbers in `calcs/shore-post/shore-post.typ`.
+
+```bash
+typst compile --root . calcs/shore-post/shore-post.typ calcs/shore-post/generated/shore-post.pdf
+typst watch --root . calcs/shore-post/shore-post.typ calcs/shore-post/generated/shore-post.pdf
+```
+
+## Hybrid
+
+Edit `calcs/concrete-beam/input.yaml`, then:
+
+```bash
+python -m pip install -r requirements.txt
+python calcs/concrete-beam/calc.py
+typst compile --root . calcs/concrete-beam/beam.typ calcs/concrete-beam/generated/beam.pdf
+```
+
+Optional output path: `python calcs/concrete-beam/calc.py path/to/input.yaml path/to/results.json`
+
+```bash
+python -m pytest calcs/concrete-beam/test_concrete_beam.py
+```
+
+`calc.py` writes named numbers. `beam.typ` does not recompute the design.
+
+## Hybrid with units (Pint)
+
+Same calculation pattern with unit-bearing YAML values. Write `span: "16 ft"`
+or `span: "192 in"`. Quote every quantity.
+
+```bash
+python calcs/concrete-beam2/calc.py
+typst compile --root . calcs/concrete-beam2/beam.typ calcs/concrete-beam2/generated/beam.pdf
+python -m pytest calcs/concrete-beam2/test_concrete_beam2.py
+```
+
+## Templates
+
+Copy one of these folders into `calcs/` and rename it. Compile from the
+`worksheets/` directory so the shared logo resolves.
+
+Typst-only:
+
+```bash
+typst compile --root . template/typst-only/main.typ template/typst-only/generated/calculation.pdf
+```
+
+Typst + Python:
+
+```bash
+python template/typst-python/calc.py
+typst compile --root . template/typst-python/main.typ template/typst-python/generated/calculation.pdf
+python -m pytest template/typst-python/test_template.py
+```
+
+## Steel beam
+
+The steel beam sheet reads section properties directly from
+`aisc-shapes-database-v15.0.xlsx`. Edit `calcs/steel-beam/input.yaml`, then:
+
+```bash
+python calcs/steel-beam/calc.py
+typst compile --root . calcs/steel-beam/beam.typ calcs/steel-beam/generated/beam.pdf
+python -m pytest calcs/steel-beam/test_steel_beam.py
+```
+
+For a standalone JSON result on stdout, use:
+
+```bash
+python calcs/steel-beam/calc.py --input calcs/steel-beam/input.yaml --stdout
+```
+
+Use `--output path/to/results.json` to select a JSON output path. The reusable
+Python function is `compute(input_dict)` in `calcs/steel-beam/calc.py`.
+
+`input.yaml` supplies the checked `Mu` and `Vu` demands. `beam.typ` determines
+and displays the gravity loads that produce those demands, and the test suite
+queries Typst metadata to verify the values match. The calculation covers
+major-axis AISC lateral torsional buckling, web shear, and point-load
+deflection. The test fixture locks the supplied `steel-beam.pdf` example for
+W6X8.5.
+
+## Wood joist
+
+The wood joist sheet reads reference design values and adjustment factors from
+`calcs/wood-joist/input.yaml`, then computes capacity checks per NDS 2018 ASD.
+
+```bash
+python calcs/wood-joist/calc.py
+typst compile --root . calcs/wood-joist/beam.typ calcs/wood-joist/generated/wood-joist.pdf
+python -m pytest calcs/wood-joist/test_wood_joist.py
+```
+
+For a standalone JSON result on stdout, use:
+
+```bash
+python calcs/wood-joist/calc.py --input calcs/wood-joist/input.yaml --stdout
+```
+
+Use `--output path/to/results.json` to select a JSON output path. The reusable
+Python function is `compute(input_dict)` in `calcs/wood-joist/calc.py`.
+
+`input.yaml` supplies the checked demands (`w`, `wL`, `M`, `V`, `R` as
+Pint-quantity strings), `span`, section dimensions, bearing geometry, NDS
+reference design values, and adjustment factors — and no longer supplies `DL`,
+`LL`, or `spacing`. `beam.typ` determines the gravity loads inline (`DL = 25
+psf`, `LL = 50 psf`, span 9 ft, spacing 13 ft), derives `w`, `wL`, `M`, `V`,
+`R`, and presents them beside the Python-checked demands; the test suite
+reconciles the two via the `<wood-joist-loads>` metadata query. `calc.py` reads
+the demands and computes section properties, flexure (with `C_L`), shear,
+bearing, and L/240 + L/360 deflection. The two deflection checks use the shared
+`check_service` helper (Acting/Allowed/Utilization); flexure, shear, and
+bearing use `check`.
+
+## Concentric footing
+
+Square concentric spread footing under axial load per ACI 318-19 — soil bearing, one-way/two-way shear, flexure, minimum steel, concrete bearing.
+
+```bash
+python calcs/concentric-footing/calc.py
+typst compile --root . calcs/concentric-footing/footing.typ calcs/concentric-footing/generated/footing.pdf
+python -m pytest calcs/concentric-footing/test_concentric_footing.py
+```
+
+For a standalone JSON result on stdout, use:
+
+```bash
+python calcs/concentric-footing/calc.py --input calcs/concentric-footing/input.yaml --stdout
+```
+
+Use `--output path/to/results.json` to select a JSON output path. The reusable
+Python function is `compute(input_dict)` in `calcs/concentric-footing/calc.py`.
+
+`input.yaml` supplies checked `Ps`/`Pu` (Pint quantities) and footing geometry/materials; `footing.typ` derives `Ps`/`Pu` inline from `DLr=10psf, LLr=20psf, Br=18.9ft, Lr=27.5ft, column 14in×14ft @145pcf` and reconciles via `<concentric-footing-loads>` query; bearing plate width `bp=6in` governs `A1`.
+
+## New calculation
+
+1. Copy the nearer example.
+2. Stay in Typst if it is arithmetic you want to see.
+3. If you need branching or iteration, write a small `calc.py` that reads YAML and writes `results.json` (`values` and `checks`).
+4. Lock one hand example in a pytest before treating the tool as stable.
+5. Extract a shared Python module only the second time you need the same procedure.