feat: add point-source light profiles

[Jammy2211]

Summary

• Add flux-conserving discrete point-source light profiles for direct image-plane emission.
• Support standard and linear-intensity variants through image evaluation, PSF convolution, galaxy aggregation, and inversion mapping matrices.
• Preserve parent-grid geometry during oversampled PSF evaluation so sub-pixel source placement remains well defined.

Closes #561

API Changes

Adds ag.lp.PointSource and ag.lp_linear.PointSource for unresolved image-plane emission.
Point-source intensity is total detector flux, conserved across light-profile over-sampling and oversampled PSF convolution.
Adds unbinned image-evaluation hooks used by composite light objects during oversampled convolution.
This does not replace ag.ps.PointFlux plus PyAutoLens's PointSolver for multiple lensed point images.
See full details below.

Test Plan

• Verify point placement, bounds, irregular-grid behavior, and flux conservation at over-sampling factors 1, 2, and 4.
• Verify sub-pixel shifts and flux conservation through oversampled PSF convolution.
• Verify Galaxy/Galaxies aggregation and linear inversion mapping-matrix behavior.
• Run python -m pytest test_autogalaxy/ -x -q (1022 passed, 5 skipped).
• Run Black and whitespace checks on the changed files.

Full API Changes (for automation & release notes)

Removed

• None.

Added

• ag.lp.PointSource(centre=(0.0, 0.0), intensity=0.1) — discrete direct image-plane emission with total-flux normalization.
• ag.lp_linear.PointSource(centre=(0.0, 0.0)) — point-source intensity solved by linear inversion.
• LightProfile.image_2d_unbinned_from(...) — evaluates over-sampled coordinates while retaining parent-grid metadata.
• Galaxy.image_2d_unbinned_from(...), Galaxies.image_2d_unbinned_from(...), and corresponding list/dict variants — propagate unbinned evaluation through composite light objects.

Changed Behaviour

• Oversampled PSF convolution now retains the parent Grid2D during profile evaluation before converting values to the convolver's fine-resolution format.
• intensity on PointSource denotes total discrete detector flux; the selected sub-pixel is scaled so mean-binning preserves that flux.

Migration

• None required for existing profiles.
• Use ag.ps.PointFlux with PyAutoLens's PointSolver when modelling multiple images produced by lensing.

Generated by the PyAutoLabs agent workflow.

[Jammy2211]

Workspace companions are ready as drafts:

• feat: add point-source imaging simulator autogalaxy_workspace#208
• test: add point-source simulator coverage autogalaxy_workspace_test#103

Both use the shared feature/point-source-light branch and carry pending-release so the library PR remains the merge gate.

[Jammy2211]

Companion workspace CI is now fully green:

• feat: add point-source imaging simulator autogalaxy_workspace#208 — Navigator + Smoke Tests passed.
• test: add point-source simulator coverage autogalaxy_workspace_test#103 — Smoke Tests passed on Python 3.12 and 3.13.

Both remain draft and pending-release behind this library PR.