chore(geometry): add angle conversion, ellipse eccentricity, polygon geometry, and triangle class

[JeelGajera]

Describe your change:

This PR adds several enhancements and new capabilities to the geometry module:

• Add Angle.to_radians() and Angle.from_radians() conversions
• Improve Ellipse.perimeter using Ramanujan’s approximation and add eccentricity property
• Extend Polygon with:
  • get_vertices() to compute vertex coordinates
  • perimeter() and area() methods
• Update Rectangle to build all 4 sides and integrate with the polygon logic
• Introduce Triangle class:
  • Validate side lengths (triangle inequality)
  • Compute interior angles (if not provided)
  • Compute perimeter and area (Heron’s formula)
• Add and adjust doctests for accuracy and coverage

These improvements expand the geometry module’s ability to model and calculate advanced shapes.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[JeelGajera]

@cclauss please review this PR.

[cclauss]

@priya-sundaram-dev, please review.

[priya-sundaram-dev]

Reviewed and ran it locally — this is a nice, well-scoped upgrade. ✅

Verified

• All doctests pass: python3 -m doctest geometry/geometry.py -v → 71 passed / 0 failed.
• ruff format --check is clean (the only ruff check hit is INP001, which is just the namespace-package rule and not something this PR introduces).
• Spot-checked the math: Ellipse(5,10).eccentricity = √(1−(b/a)²) = 0.8660…, Circle(5).eccentricity = 0.0 ✔, and the Ramanujan-II perimeter gives 48.442… ✔. Nice catch that Ramanujan reduces to 2πr for a=b, so Circle(5).perimeter stays 31.415… and doesn't regress.

Two things worth calling out in the PR description (not blockers, just so they're intentional):

1. Ellipse.perimeter changes its return value — the old π·(a+b) was only correct for circles, so this is a genuine bug-fix, but it is a behavioral change for anyone who compared against the old number. Worth a one-line note in the PR body.
2. Rectangle now stores 4 sides instead of 2 (needed so get_vertices()/shoelace area() work). Also intentional and correct, just a visible API change.

Minor, optional:

• perimeter/area are @property on Ellipse/Circle but plain methods on Polygon/Rectangle/Triangle. That inconsistency predates this PR, so no need to fix here — just flagging it since this PR adds more of the method form.
• get_vertices() raises ValueError if the polygon doesn't close; for very large polygons the 1e-6 closure tolerance could get tight under float accumulation. Fine for the current test shapes.

Overall the geometry is sound and the tests are thorough. LGTM from me — happy to re-check if you push any changes.

[priya-sundaram-dev]

Re-checked after the latest rebase/pre-commit push (69574dd) — still a clean ✅ from me.

• python3 -m doctest geometry/geometry.py -v → 71 passed / 0 failed
• ruff format --check → already formatted
• ruff check → all checks passed

CI is green across build/ruff/ty/build_docs. Nothing further needed on my end — good to merge. Nice work @JeelGajera.