EIS: add surface form override

[MarcBerliner]

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context.

Fixes # (issue)

Type of change

Add an entry under # [Unreleased] in CHANGELOG.md, in one of ## Breaking changes, ## Deprecated, ## Features, or ## Bug fixes (include PR number; breaking and deprecation entries need a one-line migration note). Internal-only PRs — refactor, docs, CI, tests — can skip this. See RELEASE.md for the full policy.

Important checks:

Please confirm the following before marking the PR as ready for review:

• No style issues: nox -s pre-commit
• All tests pass: nox -s tests
• The documentation builds: nox -s doctests
• Code is commented for hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.19%. Comparing base (8013d49) to head (477e9e4).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5632   +/-   ##
=======================================
  Coverage   98.19%   98.19%           
=======================================
  Files         339      339           
  Lines       32069    32071    +2     
=======================================
+ Hits        31489    31492    +3     
+ Misses        580      579    -1     

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