Docstrings missing for `hyp.manip` and ~150 internal classes/methods across `align/`, `predict/`

[jeremymanning]

Imported from jeremymanning#28

Original request: "all doc strings need to be added. some can be copied over (and/or lightly modified) from the prior version of the toolbox."

Current status (verified 2026-07-07 against the 1.0 branch):

The top-level public API is in good shape — hyp.plot, hyp.reduce, hyp.align, hyp.normalize, hyp.cluster, hyp.describe, and hyp.load all have substantial docstrings (1177–44412 characters).

An AST scan of every public (non-underscore) function/class definition in the hypertools package (excluding _externals/) found:

TOTAL public defs: 305, MISSING docstring: 152

Missing docstrings are concentrated in:

• hypertools/align/align.py, align/null.py, align/hyperalign.py, align/common.py (Aligner, fit, transform, fit_transform), align/srm.py (all fitter/transformer/*_fitter closures and __init__s)
• hypertools/predict/{laplace,kalman,gp,common,autoreg,chronos,arima}.py (every fitter/forecaster/__init__, and Forecaster.__init__/.fit/.predict/.fit_predict)
• hypertools/_shared/helpers.py (center, scale, group_by_category, interp_array, interp_array_list, parse_args, parse_kwargs, reshape_data, convert_text)
• hypertools/external/{ppca,brainiak}.py
• hyp.manip — the newest public dispatcher function, added most recently, currently has __doc__ is None

>>> import hypertools as hyp
>>> hyp.manip.__doc__ is None
True

Suggested next step: a documentation pass adding docstrings to the above, prioritizing hyp.manip (public-facing, zero coverage) and the align/predict module internals (used by advanced users constructing custom pipelines).