JOSS paper: paper.md + paper.bib (#101)

[neuromechanist]

Closes #101.

Summary

Adds the Journal of Open Source Software (JOSS) submission for pyAMICA: paper.md
(~880 words) and paper.bib (17 references, all DOIs verified). Also addresses
repository items a JOSS reviewer checks alongside the paper.

What is included

• paper.md: Summary, Statement of need, Implementation and validation, State
  of the field, Acknowledgements. Sole author (S. Y. Shirazi), SCCN/UCSD.
• paper.bib: AMICA (Palmer et al.), natural gradient (Amari), Newton-ICA
  (Palmer et al. 2008), ICLabel, EEGLAB, Infomax, extended Infomax, FastICA,
  Picard, MNE, PyTorch, NumPy, SciPy, MLX, and the two other Python AMICA
  reimplementations. All journal DOIs resolved against the publisher.
• README: de-WIP'd; reflects validated Fortran parity, GPU backends, docs;
  install via uv sync.
• getting-started: install from source (a PyPI release name is deferred).
• LICENSE: copyright year 2023-2026.
• sample_data/ATTRIBUTION.md: provenance/licenses for the bundled SCCN/EEGLAB
  test artifacts (Fortran binary, sample EEG, loadmodout15.m).

Process (per the no-shortcuts standard)

• Drafted with the manuscript-writing skill; polished with humanizer.
• Independent paper-review (JOSS reviewer). Findings addressed: the novelty
  claim was reframed after a landscape check found two other public Python AMICA
  packages (now cited); missing methods citations added (natural gradient,
  Newton-ICA, ICLabel); the drop-in claim scoped to single-model (multi-model
  round-trips with a self-consistent layout); the test-suite wording corrected
  to "synthetic data is never the basis of a correctness claim"; "dipolar"
  glossed for non-specialists.

Remaining before actual JOSS submission (author action)

• ORCID: paper.md still has a placeholder; the corresponding author's real
  ORCID must replace it.
• Archived release (Zenodo/Software Heritage) with a matching version, and
  the PyPI distribution name, to be arranged at the transfer/release step.

Tested: paper is not code; all 17 citation keys resolve to bib entries; docs
build is exercised by the existing docs workflow.

[neuromechanist]

Updated per author request:

• Co-authors added: Arnaud Delorme (ORCID 0000-0002-0799-3557; SCCN/UCSD + CNRS, University of Toulouse) and Scott Makeig (ORCID 0000-0002-9048-8438; SCCN/UCSD) added to paper.md and CITATION.cff. Makeig moved from the acknowledgements to the author list; the acknowledgement now credits Palmer and Kreutz-Delgado.
• Corresponding-author ORCID set to the real value (0000-0001-5557-259X).
• README modernized: leads with the scikit-learn AMICA API, a backend/precision guide (CPU/CUDA float64, float32, MLX on Apple Silicon), and the EEGLAB write_amica_output/loadmodout15 round-trip; the legacy NumPy CLI is kept as a subsection and the full parameter reference points to the docs.

Remaining before actual JOSS submission (release/transfer step): an archived release (Zenodo/Software Heritage) with a matching version, and the PyPI distribution name (deferred).