feat: support array targeting and evaluation diagnostics

[roncohen]

Summary

Port the relevant array-targeting and diagnostic changes from the Node SDK (JavaScript PRs #711, #714, and #724):

• Preserve native arrays as evaluation leaves, with membership, singleton equality, intersection, and empty-array semantics; retain scalar behavior and legacy FlattenJson behavior.
• Fail entire invalid rules closed, including under negation and otherwise-matching OR groups, while allowing subsequent rules to match.
• Produce deduplicated missing-field and unsupported-array diagnostics; rate-limit warnings independently of user context.
• Send evalErrors in check telemetry and evaluationErrors in bootstrap JSON, retaining legacy missing-field metadata.
• Match JavaScript's Unicode/HTML-sensitive escaping for composite-array comparisons. An inline comment explains why the relaxed encoder is appropriate for internal comparison strings and notes remaining number-formatting/key-ordering parity limits.
• Add regression coverage and document array semantics, diagnostics, and application-owned shutdown.

Canonical context deduplication is intentionally a separate, independent PR. This SDK has no remote evaluation/config-check API; the Node signal-interception fix requires no .NET lifecycle change.

Release prerequisite

Do not release until the ingest service supports evalErrors, matching the rollout prerequisite in JavaScript PR #724. Invalid rules that previously matched through negation/OR now fail closed; this behavior change is documented.

Validation

• dotnet build dotnet-sdk.sln -c Release: zero warnings/errors; library builds for .NET 10 and .NET Standard 2.0.
• dotnet test dotnet-sdk.sln -c Release --no-build: 332 passed (161 SDK + 5 example tests on each of .NET 8 and .NET 10).
• Regression coverage includes serialized bootstrap diagnostic field names, telemetry compatibility, warning deduplication, and composite-array escaping.
• git diff --check passed.

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