Add regression tests for null and duplicate type fields in provider-message decoder

[numinousmuses]

Trigger

Requested work to pin the decoded semantics of duplicate and null type fields in the Darkbloom provider-message decoder. A duplicate or case-variant type key pushes decoding off the fast path onto Go's encoding/json rules, and this behavior deserves an explicit regression test rather than relying on the decoder as its own oracle.

Behavior under test

The new test file coordinator/protocol/messages_type_null_duplicate_test.go adds TestProviderMessageTypeNullAndDuplicateFields, a table test with five cases and explicit expected outcomes:

• known type then null (null is a no-op, prior string kept)
• null then known type (later string wins)
• mixed-case null duplicate (case-insensitive matching, prior string kept)
• unknown type then null (still rejected)
• numeric duplicate then known type (wrong JSON type still fails the whole decode)

Accepted heartbeat cases assert the decoded Type and Status; rejection cases assert the decode fails. The change is test-only; no production code was modified.

Verification

Both configured checks passed on this revision:

• Protocol behavior (265 tests, provider-message decoder and protocol regressions only; does not cover Forge infrastructure or conversations)
• Documentation

The agent additionally reported running the named test and the full protocol suite under the race detector locally, plus make docs-check; those local results are not independent verification. A pass here establishes these tests passed on this revision, not that the decoder is free of other issues.

Review focus

Confirm the expected types and acceptance outcomes match the intended encoding/json semantics, particularly that JSON null is treated as a no-op and a numeric type rejects even with a later valid duplicate.

Before/After

flowchart TD
  subgraph Before
    A[Existing protocol tests] --> B[ProviderMessage.UnmarshalJSON]
  end
  subgraph After
    C[TestProviderMessageTypeNullAndDuplicateFields] --> D[ProviderMessage.UnmarshalJSON]
    D --> E[5 explicit cases: last-match-wins, case-insensitive, null no-op, numeric reject]
  end

Loading

Closes #15. The issue's status comment tracks the requested work.

Independent checks configured: Protocol behavior, Documentation.

Recorded check	Result
Protocol behavior	Passed
Documentation	Passed

Source revision a9d9ca55b4dc. Verification status comes from execution records; agent observations are provisional.

The proposed change passed independent verification. PR CI checks its merge with the target branch separately. Maintainers review the behavior and decide what ships.

Verification reference

Source: a9d9ca55b4dc3236f3c2491b22371396a922c836
Verified tree: d1602cb7555e880fd87d7f209b6f7aee96039646
Task: c0b3ce44f544dcd1a4c2bd4daa506314

[numinousmuses]

Numinous Forge · Merged into this fork

Trigger: Instructed

This PR has been merged. The recorded checks passed on its reviewed revision.

Next: No further action on this PR.

Verification details

Recorded check	Result
Protocol behavior	Passed
Documentation	Passed
Coordinator	Passed

Source revision 9d02805008ef. Verification status comes from execution records; agent observations are provisional.

This run verifies the PR and does not modify its code.