test(codecs): add native codec compatibility coverage

[pront]

Summary

Motivation

Native codec tests currently rely on large historical fixture snapshots for both current round-trip behavior and backward compatibility. Before removing that fixture machinery in a separate PR, establish explicit replacement coverage that distinguishes those two jobs.

Changes

• add 1,000-case in-memory canonicalization property tests for native JSON and Protobuf
• add frozen protobuf wire payloads for pre-v24 metric variants, pre-v0.27 tags, pre-v34 metadata, and pre-v41 missing source event IDs
• generate JSON-safe logs, metrics, traces, metadata, tags, and values with a dedicated proptest strategy
• keep the replacement tests independent of the fixture generator's QuickCheck implementation
• retain every historical fixture, fixture test, generator binary, feature, and runtime compatibility path unchanged

Fixture removal is intentionally deferred to a follow-up PR.

References

None.

Vector configuration

Not applicable; this adds test coverage only.

How did you test this PR?

• cargo test -p codecs --test native — 18 passed, including the existing fixture suite and 2,000 generated cases; 5 ignored
• cargo test -p vector-core event::proto::tests — 4 passed
• cargo check -p vector-core --features generate-fixtures --bin generate-fixtures
• cargo clippy -p codecs --test native -- -D warnings
• cargo fmt --all -- --check

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

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[chatgpt-codex-connector]

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-29T01:25:31.642905Z	da08ead	New commits

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