semi implemented and features implemented save checkpoint

docs/features/unchecked/attestor/rfc-8785-canonical-json-serialization.md

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+# RFC 8785 Canonical JSON Serialization
+
+## Module
+Attestor
+
+## Status
+IMPLEMENTED
+
+## Description
+Full RFC 8785 JSON canonicalizer with decimal point, number serialization, string normalization, and write method implementations. Verified by determinism property-based tests and canonical JSON test suite.
+
+## Implementation Details
+- **RFC 8785 JSON Canonicalizer**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Json/Rfc8785JsonCanonicalizer.cs` -- main canonicalizer implementing RFC 8785 (JSON Canonicalization Scheme / JCS).
+- **Decimal Point Handling**: `Json/Rfc8785JsonCanonicalizer.DecimalPoint.cs` -- handles decimal point normalization per RFC 8785 rules (no trailing zeros, no unnecessary decimal points).
+- **Number Serialization**: `Json/Rfc8785JsonCanonicalizer.NumberSerialization.cs` -- deterministic number serialization (IEEE 754 compliance, consistent exponent notation).
+- **String Normalization**: `Json/Rfc8785JsonCanonicalizer.StringNormalization.cs` -- Unicode normalization, escape sequence handling, and surrogate pair processing per RFC 8785.
+- **Write Methods**: `Json/Rfc8785JsonCanonicalizer.WriteMethods.cs` -- deterministic JSON writing (sorted object keys, no whitespace, consistent separators).
+- **Schema Validation Result**: `Json/SchemaValidationResult.cs` -- result of validating canonicalized JSON against a schema.
+- **Schema Validation Error**: `Json/SchemaValidationError.cs` -- individual validation error.
+- **Content-Addressed ID Generator**: `Identifiers/ContentAddressedIdGenerator.cs` -- uses canonicalized JSON for deterministic SHA-256 ID generation.
+- **Tests**: `__Tests/StellaOps.Attestor.ProofChain.Tests/Rfc8785JsonCanonicalizerTests.cs`, `DeterminismTests.cs`
+
+## E2E Test Plan
+- [ ] Canonicalize a JSON object with unsorted keys and verify output has lexicographically sorted keys
+- [ ] Canonicalize numbers with trailing zeros (e.g., 1.0000) and verify output removes unnecessary precision per RFC 8785
+- [ ] Canonicalize strings with Unicode characters and verify proper Unicode normalization and escape sequences
+- [ ] Canonicalize the same JSON object twice and verify byte-identical output
+- [ ] Canonicalize a JSON object with different whitespace formatting and verify identical canonicalized output
+- [ ] Canonicalize a number requiring scientific notation and verify consistent exponent representation
+- [ ] Generate a content-addressed ID from canonicalized JSON and verify it is deterministic across runs
+- [ ] Run the RFC 8785 test vectors (from the specification) and verify all pass