Fix source plotting scale bug

[shimwell]

Description

The source points can outside the requested plot width and currently expand the axis limits.

Fixing this by setting the limits after drawing the scatter

AI Assistance

Code changes done by a human but I got GPT-6.1 Sol to review it.

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 18) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

Summary by CodeRabbit

• Bug Fixes
  • Plot views now retain the requested x/y limits, preventing sampled source points outside the view from expanding the axes.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 9f53c0ae-61a3-4f32-ac04-333b83a430b9

📥 Commits

Reviewing files that changed from the base of the PR and between aa4afc4 and 5983e8d.

📒 Files selected for processing (1)

• openmc/model/model.py

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📝 Walkthrough

Model.plot now applies the requested x and y limits after plotting and source-point sampling in all outline modes. The outline-only path continues to set an equal aspect ratio.

Changes: Model plot axis limits

Layer / File(s)	Summary
Apply requested axis limits openmc/model/model.py	The outline-only branch retains equal aspect ratio. After plotting and source-point sampling, plot sets the requested x and y limits regardless of outline mode.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix

Suggested reviewers: paulromano

Merge Risk: ⚪ Minimal · up to 5983e

The requested bounds are applied after plotting and source sampling, addressing the reported axis expansion. No concrete merge-blocking regression is established.

Pre-merge checks · 5

Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 1 files.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description check		The description explains the source plotting bug and the fix. It discloses AI assistance and records the relevant checklist items. It does not identify an issue number, specify the AI harness or reaso…
Title check		The title clearly and concisely identifies the main change: fixing the source plotting scale bug.

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[shimwell]

I have also been testing locally with this script

import matplotlib.pyplot as plt
import openmc

sphere = openmc.Sphere(r=10.0, boundary_type="vacuum")
model = openmc.Model(geometry=openmc.Geometry([
    openmc.Cell(region=-sphere)
]))
model.settings.source = openmc.IndependentSource(
    space=openmc.stats.Point((8.0, 0.0, 0.0))
)

fig, axes = plt.subplots(1, 2, figsize=(10, 4))
for ax, n_samples, title in zip(
    axes, [None, 1], ["Without source overlay", "With source overlay"]
):
    model.plot(
        origin=(0, 0, 0), width=(4, 4), pixels=(100, 100),
        n_samples=n_samples, axes=ax,
        source_kwargs={"color": "red", "s": 100},
    )
    ax.set_title(title)
    ax.set_xlabel("x [cm]")
    ax.set_ylabel("y [cm]")
    print(title, "x limits:", ax.get_xlim(), "y limits:", ax.get_ylim())

fig.tight_layout()
plt.show()

[coderabbitai]

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[paulromano]

Thanks @shimwell!