fix(filter): reject unknown config fields

[gnanirahulnutakki]

Change Summary

Reject unknown top-level fields in processor:filter configuration so --validate-and-exit catches typos instead of silently discarding them.

The filter processor already registers validate_typed_config::<Config>, but its typed config was the exception among strict engine and component schemas because it did not use Serde's deny_unknown_fields. This adds that schema contract and a focused regression test that verifies the offending field is named in the diagnostic.

What issue does this PR close?

• Closes Config validation (--validate-and-exit) accepts invalid processor:filter config with unknown keys #3568

How are these changes tested?

• cargo +1.96.1 check -p otap-df-core-nodes
• cargo +1.96.1 test -p otap-df-core-nodes rejects_unknown_top_level_field -- --nocapture
• Before/after df_engine --validate-and-exit reproduction using the issue configuration
• python3 tools/sanitycheck.py
• Changelog validation with the repository-pinned chloggen v0.30.0
• cargo +1.96.1 xtask check

Are there any user-facing changes?

Yes. Invalid filter processor configuration now fails validation with an explicit unknown-field error instead of being accepted.

Changelog

• Added a .chloggen/*.yaml entry
• This PR is a chore (indicated in title)
• This is a documentation-only PR.

AI tooling assisted with code navigation and drafting; the behavior was reproduced and the full repository-required validation suite was run by the contributor.

[linux-foundation-easycla]

• ❌ The email address for the commit (a3b0679) is not linked to the GitHub account, preventing the EasyCLA check. Consult this Help Article and GitHub Help to resolve. (To view the commit's email address, add .patch at the end of this PR page's URL.) For further assistance with EasyCLA, please visit our EasyCLA portal and chat with our support bot.

[opentelemetry-pr-dashboard]

Pull request dashboard status

Status last refreshed: 2026-07-26 19:03:32 UTC.

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[lquerel]

Thanks

[lquerel]

@gnanirahulnutakki could you sign the CLA and mark the PR ready for review.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.91%. Comparing base (cbc8dd8) to head (a3b0679).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3572      +/-   ##
==========================================
- Coverage   86.91%   86.91%   -0.01%     
==========================================
  Files         782      782              
  Lines      319143   319150       +7     
==========================================
- Hits       277389   277386       -3     
- Misses      41230    41240      +10     
  Partials      524      524              

Components	Coverage Δ
otap-dataflow	87.98% <100.00%> (-0.01%)	⬇️
query_engine	89.57% <ø> (ø)
otel-arrow-go	52.45% <ø> (ø)
quiver	92.20% <ø> (ø)

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[gnanirahulnutakki]

Marked the PR ready for review. EasyCLA is now the only remaining gate; it is still blocked because the commit email needs to be linked and verified on my GitHub account before I can complete the contributor agreement.