JOSS 2.0 paper: 4th pass + bib refs + draft PDF workflow

- Comprehensive paper revision: capability table, architecture paragraph,
  spectral in family list, expanded Research Impact (docs/tutorials/license/
  PySINDy), updated AI disclosure, three-step usage description
- Add kalman1960, ahnert2007, pysindy references to paper.bib
- Add .github/workflows/draft-pdf.yml to compile JOSS draft PDF on push

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: pavelkomarov

.github/workflows/draft-pdf.yml

@@ -0,0 +1,19 @@
+on: [push]
+
+jobs:
+  paper:
+    runs-on: ubuntu-latest
+    name: Paper Draft
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Build draft PDF
+        uses: openjournals/openjournals-draft-action@master
+        with:
+          journal: joss
+          paper-path: paper/paper.md
+      - name: Upload
+        uses: actions/upload-artifact@v4
+        with:
+          name: paper
+          path: paper/paper.pdf

paper/paper.bib

@@ -120,3 +120,36 @@ @software{derivative_pkg
   year      = {2021},
   url       = {https://github.com/andgoldschmidt/derivative}
 }
+
+@article{kalman1960,
+  author  = {Rudolf E. Kalman},
+  title   = {A new approach to linear filtering and prediction problems},
+  journal = {Journal of Basic Engineering},
+  year    = {1960},
+  volume  = {82},
+  number  = {1},
+  pages   = {35--45},
+  doi     = {10.1115/1.3662552}
+}
+
+@article{ahnert2007,
+  author  = {Karsten Ahnert and Markus Abel},
+  title   = {Numerical differentiation of experimental data: local versus global methods},
+  journal = {Computer Physics Communications},
+  year    = {2007},
+  volume  = {177},
+  number  = {10},
+  pages   = {764--774},
+  doi     = {10.1016/j.cpc.2007.03.009}
+}
+
+@article{pysindy,
+  author  = {Brian M. de Silva and Kathleen Champion and Markus Quade and Jean-Christophe Loiseau and J. Nathan Kutz and Steven L. Brunton},
+  title   = {{PySINDy}: A {Python} package for the sparse identification of nonlinear dynamics from data},
+  journal = {Journal of Open Source Software},
+  year    = {2020},
+  volume  = {5},
+  number  = {49},
+  pages   = {2104},
+  doi     = {10.21105/joss.02104}
+}