Add ProjectSpectralFilter AMR projector

[nilsdeppe]

Proposed changes

Only the AMR projector is new in this PR.

Upgrade instructions

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.
• If a coding agent is used, have one of
  "Co-Authored-By: Claude Sonnet 4.6 noreply@anthropic.com",
  "Co-Authored-by: Codex noreply@openai.com", or
  "Co-Authored-By: GitHub Copilot CLI noreply@microsoft.com"
  as the last line of the commit, depending on the agent.

Further comments

[michaeldmurphy1]

The code supports (initial) radial refinement of B1, B2, and B3 (see here). Eventually this logic will need to be included for these operations.

This would mean both splitting and joining of these pairs of topologies

• Cylinder $\leftrightarrow$ Cylinder + Hollow Cylinder
• Ball $\leftrightarrow$ Ball + Spherical Shell

This probably does not matter yet as the Bn radial refinement is not currently in any AMR logic.

[nilsdeppe]

Yea, how to deal with h-refinement in these topology changing splits is something Larry, Will, and I have discussed a bit but haven't gotten consensus on. Probably we will try a few different things to see what works. We are ignoring issues related to that for now. I think we should hit an error that no filter is applied in an element

[kidder]

I have no requested changes and will approve after the dependent PR is in

[nilsdeppe]

I've rebased this on the changes from #7285

The merge-base changed after approval.