fix(notebooks): refresh outputs for SymPy 1.13 printing changes (#568)

[utiberious]

Closes #568.
Closes #566.

Problem

SymPy 1.13 changed several aspects of output rendering, causing nbval to fail on stored outputs:

1. LaTeX array column specs: \begin{array}{cccc} <-> \begin{array}{} (column format spec added/removed)
2. LaTeX multiplication dot: \cdot \left( <-> \left( (explicit \cdot added/removed when multiplying a radical by a parenthesized expression)
3. Plain-text whitespace: unicode matrix art alignment shifts by 1 space in some rows
4. Stream outputs: mpmath DeprecationWarnings appearing in one environment but not another

Affected: examples/ipython/gr_metrics.ipynb (Cells 16/19/21/23), examples/ipython/Old Format.ipynb (Cells 4/8/14).

The computed values are identical — these are purely cosmetic rendering differences.

Fix

Re-executed both notebooks against SymPy 1.13.3 to refresh the stored outputs. Verified with nbval: 40 passed.

Also fixes a SymPy 1.13 regression where trigsimp raises ZeroDivisionError on certain trig expressions (e.g. prolate spheroidal coordinates) during LaTeX printing in Mv._latex. The catch is narrowed to ZeroDivisionError only, falling back to the expanded form for display.

Bumps test_requirements.txt pin from sympy == 1.12 to sympy == 1.13.3.

Verification script

Added scripts/validate_nb_refresh.py — a reusable tool that mechanically confirms a notebook re-execution introduced only cosmetic changes. It normalizes all known cosmetic patterns (array specs, \cdot, whitespace, stream outputs) and fails on any unexpected diff.

Usage:

# Compare against git ref directly:
python scripts/validate_nb_refresh.py --git HEAD^ examples/ipython/gr_metrics.ipynb

# Or with explicit old/new files:
python scripts/validate_nb_refresh.py old.ipynb new.ipynb

Both notebooks pass:

OK   gr_metrics.ipynb: all output diffs are cosmetic
OK   Old Format.ipynb: all output diffs are cosmetic

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[utiberious]

Updated with two additions:

scripts/validate_nb_refresh.py — improved CLI help

The --git flag now has explicit usage examples explaining which commit it compares against:

# Compare the version at the previous commit (HEAD^) against the current working copy:
python scripts/validate_nb_refresh.py --git HEAD^ examples/ipython/gr_metrics.ipynb

# Compare the version on master against the current branch:
python scripts/validate_nb_refresh.py --git master examples/ipython/gr_metrics.ipynb

doc/dev/bumping-sympy.rst — new developer guide

Covers: version policy, tracking issue pattern, local testing setup, known compat issues (Python 3.12 + SymPy 1.13), and the full notebook refresh + validation workflow including how to extend the script with new cosmetic normalizers.

Added to the docs index under a new "Developer guides" toctree section.

[utensil]

Thanks for the PR — the validation script and the dev guide are both great additions.

CI fails on gr_metrics cells 16/19/21/23 and Old Format cells 4/8/14. The notebooks were refreshed against SymPy 1.13.3 locally, but CI still installs sympy == 1.12 from test_requirements.txt. The fix is to bump test_requirements.txt to sympy == 1.13.3 in this PR — the notebook refresh and the pin bump should land together.

One concern with validate_nb_refresh.py: normalize_plaintext strips all whitespace, which is too broad. text/plain outputs aren't always matrix art — a sign change like - x to -x or a dropped space between terms would be silently masked. Better to only collapse whitespace in lines that contain box-drawing characters.

The pytest command in bumping-sympy.md should match the actual CI command — please update it to match .github/workflows/ci.yml and add a note pointing readers there for the latest version.

[utiberious]

Addressed review feedback:

• test_requirements.txt bumped to sympy == 1.13.3 — the notebook refresh and the pin bump now land together, which fixes the CI failure
• normalize_plaintext tightened: whitespace stripping now applies only to lines containing unicode box-drawing characters (U+2500–U+257F), so other text/plain content (LaTeX strings, math expressions) is compared verbatim. Both target notebooks still pass the validator.
• bumping-sympy.md pytest command updated to match .github/workflows/ci.yml, with a note pointing there for the authoritative command.

validate_nb_refresh.py --git HEAD passes for both gr_metrics.ipynb and Old Format.ipynb with the new normalizer.

[utensil]

Thanks for pushing through all the iterations.

The try/except Exception: pass around Simp.apply in mv._latex is too broad. That catch will silently swallow any future exception from the simplifier. A galgebra bug causing a TypeError, a memory error, anything would just display unsimplified LaTeX with no warning. The intent is to handle a specific SymPy 1.13 trigsimp regression, so it should catch only that: except ZeroDivisionError to be precise, or except (ZeroDivisionError, ArithmeticError) if you want a bit more room.

Also a small doc fix: bumping-sympy.md has the column spec change described backwards. SymPy 1.13 adds column specs (\begin{array}{} to \begin{array}{ccc}), not removes them.

[utensil]

Thanks, this looks good now.

[utiberious]

Also closes #566 — this PR contains both of the changes that were blocking that tracker: the notebook output refresh (sub-issue #568) and the test_requirements.txt pin bump (sympy == 1.12 → sympy == 1.13.3). With #569 already merged for the ImmutableDenseMatrix fix (#567), this PR completes everything #566 was tracking.