Assert that forked upstream dependencies are absent

[masih]

Sei forked a set of upstream dependencies, and all of those are flattened into a single go module.

Depending on the remote ones is almost certainly a programmer error. Assert that they are absent to avoid accidental external dependency.

[github-actions]

The latest Buf updates on your PR. Results from workflow Buf / buf (pull_request).

Build	Format	Lint	Breaking	Updated (UTC)
✅ passed	✅ passed	✅ passed	✅ passed	Apr 10, 2026, 1:46 PM

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.02%. Comparing base (107c8e7) to head (424f43d).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3226      +/-   ##
==========================================
- Coverage   59.03%   59.02%   -0.01%     
==========================================
  Files        2065     2065              
  Lines      169424   169413      -11     
==========================================
- Hits       100021   100001      -20     
- Misses      60653    60659       +6     
- Partials     8750     8753       +3     

Flag	Coverage Δ
sei-db	70.41% <ø> (ø)

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see 29 files with indirect coverage changes

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