Improved Pattern.draw_graph visualization

[CodeMaverick2]

Before submitting, please check the following:

• Make sure you have tests for the new code and that test passes (run nox)
• If applicable, add a line to the [unreleased] part of CHANGELOG.md, following keep-a-changelog.
• Format added code by ruff
  • See CONTRIBUTING.md for more details
• Make sure the checks (github actions) pass.

Then, please fill in below:

Context (if applicable):

• The current draw_graph uses color-only node differentiation, dashed lines for both edges and layer separators (causing visual confusion), and has no angle display or legend.

Description of the change:

• Node shapes follow MBQC literature conventions: squares for inputs, filled circles for measured, empty circles for outputs
• Replaced vertical dashed layer separators with gray labels and a "Measurement order" arrow
• Graph edges are light dashed lines; correction arrows remain solid — clear visual hierarchy
• Added show_measurements parameter to display measurement labels (plane + angle in units of π)
• Added show_legend parameter for node/edge type legend
• Added _format_measurement_label static method with unit tests
• Regenerated baseline images

From issue -

Generated with PR changes -

The first image (before) is the example from the issue; the second (after) is the same pattern rendered with this PR.
Inputs (node 1) are now squares instead of red circles, measured nodes are filled black, Pauli-measured nodes (node 3) are blue, and outputs (2, 6, 7) are empty circles.
Dashed layer separators are replaced by a horizontal arrow with layer labels.
Measurement labels show plane and angle (e.g. XZ(π/10)).
Graph edges (light dashed) are visually distinct from correction arrows (solid). A legend explains all visual elements.

Related issue:
#387

[codecov]

Codecov Report

❌ Patch coverage is 95.38462% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.82%. Comparing base (03a89c9) to head (d3adee9).

Files with missing lines	Patch %	Lines
graphix/visualization.py	95.38%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #444      +/-   ##
==========================================
+ Coverage   88.76%   88.82%   +0.06%     
==========================================
  Files          44       44              
  Lines        6308     6343      +35     
==========================================
+ Hits         5599     5634      +35     
  Misses        709      709              

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[CodeMaverick2]

CI fails on Python 3.10–3.13 due to a pre-existing bug in the veriphix reverse dependency, unrelated to this PR. Passes on Python 3.14 because veriphix is excluded from that version. All graphix tests and other reverse dependencies pass.

[thierry-martinez]

Veriphix CI is now fixed. It's all green now!

[CodeMaverick2]

Hey @thierry-martinez, could someone from the team please review my PR and let me know if any changes are required