semi implemented and features implemented save checkpoint

docs/features/unchecked/concelier/deterministic-semantic-merge-hash-for-advisory-deduplication.md

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+# Deterministic Semantic Merge Hash for Advisory Deduplication
+
+## Module
+Concelier
+
+## Status
+IMPLEMENTED
+
+## Description
+Computes identity-based semantic hash from (CVE + PURL/CPE + version-range + CWE + patch_lineage) for cross-distro advisory deduplication. Includes normalizers (PURL, CPE, version range, CWE, patch lineage), golden corpus validation (Debian/RHEL/SUSE/Alpine), fuzzing tests (1000 random inputs), shadow-write migration mode, and backfill service. Distinct from "Advisory Ingestion with Canonical Deduplication" which is the overall dedup concept; this is the specific merge_hash identity algorithm.
+
+## Implementation Details
+- **Modules**: `src/Concelier/__Libraries/StellaOps.Concelier.Merge/Identity/`, `src/Concelier/__Libraries/StellaOps.Concelier.Merge/Services/`, `src/Concelier/__Libraries/StellaOps.Concelier.Merge/Jobs/`
+- **Key Classes**:
+  - `MergeHashCalculator` (`src/Concelier/__Libraries/StellaOps.Concelier.Merge/Identity/MergeHashCalculator.cs`) - computes deterministic semantic hash from (CVE + PURL/CPE + version-range + CWE + patch_lineage) with input normalizers
+  - `MergeHashShadowWriteService` (`src/Concelier/__Libraries/StellaOps.Concelier.Merge/Identity/MergeHashShadowWriteService.cs`) - shadow-write mode for migration validation
+  - `MergeHashBackfillService` (`src/Concelier/__Libraries/StellaOps.Concelier.Merge/Services/MergeHashBackfillService.cs`) - retroactive backfill of merge hashes for existing advisories
+  - `MergeHashBackfillJob` (`src/Concelier/__Libraries/StellaOps.Concelier.Merge/Jobs/MergeHashBackfillJob.cs`) - scheduled `IJob` for backfill execution
+- **Interfaces**: `IMergeHashCalculator`
+- **Source**: SPRINT_8200_0012_0001_CONCEL_merge_hash_library.md
+
+## E2E Test Plan
+- [ ] Compute merge hash for two semantically identical advisories from different sources (e.g., Debian and RHEL for same CVE) and verify identical hash output
+- [ ] Verify PURL normalization: different PURL formats for the same package produce the same merge hash
+- [ ] Verify CPE normalization: equivalent CPE strings produce identical hashes
+- [ ] Verify determinism: same input produces the same hash across 1000 repeated computations
+- [ ] Verify golden corpus: validate merge hash against the golden corpus of known Debian/RHEL/SUSE/Alpine advisories
+- [ ] Verify shadow-write mode: enable shadow writes and confirm both old and new hashes are persisted for comparison
+- [ ] Verify backfill: run `MergeHashBackfillJob` and confirm pre-existing advisories receive computed merge hashes