CI: test new "slim" runner variants

[shenanigansd]

Packaging and publishing was left out for security reasons, and benchmarks were skipped for now for performance reasons.

[codspeed-hq]

Merging this PR will improve performance by 11.08%

⚡ 1 improved benchmark
✅ 1 untouched benchmark

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
⚡	test_stutter[0.0-cats are small-cats are small]	129.4 µs	116.5 µs	+11.08%

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_{Comparing br/slim (0d54d1d) with main (a2d61a1)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.29%. Comparing base (a2d61a1) to head (0d54d1d).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #141   +/-   ##
=======================================
  Coverage   88.29%   88.29%           
=======================================
  Files           3        3           
  Lines          94       94           
=======================================
  Hits           83       83           
  Misses         11       11           

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[Copilot]

Pull request overview

This PR migrates GitHub Actions CI workflows from standard ubuntu-latest runners to new ubuntu-slim runner variants for testing purposes. As noted in the description, packaging/publishing workflows and benchmark workflows are intentionally excluded for security and performance reasons respectively.

Changes:

• Updated 3 jobs in the Python CI workflow (lint, test, codecov) to use ubuntu-slim
• Updated the deploy job in the docs workflow to use ubuntu-slim
• Updated the dependency review workflow to use ubuntu-slim

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/python-ci.yaml	Migrated all three jobs (lint, test, codecov) from ubuntu-latest to ubuntu-slim
.github/workflows/docs.yaml	Migrated the deploy job from ubuntu-latest to ubuntu-slim
.github/workflows/dependency-review.yaml	Migrated the dependency-review job from ubuntu-latest to ubuntu-slim

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

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