Add reference architecture and testing strategy documentation

- Created a new document for the Stella Ops Reference Architecture outlining the system's topology, trust boundaries, artifact association, and interfaces.
- Developed a comprehensive Testing Strategy document detailing the importance of offline readiness, interoperability, determinism, and operational guardrails.
- Introduced a README for the Testing Strategy, summarizing processing details and key concepts implemented.
- Added guidance for AI agents and developers in the tests directory, including directory structure, test categories, key patterns, and rules for test development.

docs/product-advisories/archived/2025-12-21-binaryindex/README.md

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+# Archived Advisory: Mapping Evidence Within Compiled Binaries
+
+**Original Advisory:** `21-Dec-2025 - Mapping Evidence Within Compiled Binaries.md`
+**Archived:** 2025-12-21
+**Status:** Converted to Implementation Plan
+
+---
+
+## Summary
+
+This advisory proposed building a **Vulnerable Binaries Database** that enables detection of vulnerable code at the binary level, independent of package metadata.
+
+## Implementation Artifacts Created
+
+### Architecture Documentation
+
+- `docs/modules/binaryindex/architecture.md` - Full module architecture
+- `docs/db/schemas/binaries_schema_specification.md` - Database schema
+
+### Sprint Files
+
+**Summary:**
+- `docs/implplan/SPRINT_6000_SUMMARY.md` - MVP roadmap overview
+
+**MVP 1: Known-Build Binary Catalog (Sprint 6000.0001)**
+- `SPRINT_6000_0001_0001_binaries_schema.md` - PostgreSQL schema
+- `SPRINT_6000_0001_0002_binary_identity_service.md` - Identity extraction
+- `SPRINT_6000_0001_0003_debian_corpus_connector.md` - Debian/Ubuntu ingestion
+
+**MVP 2: Patch-Aware Backport Handling (Sprint 6000.0002)**
+- `SPRINT_6000_0002_0001_fix_evidence_parser.md` - Changelog/patch parsing
+
+**MVP 3: Binary Fingerprint Factory (Sprint 6000.0003)**
+- `SPRINT_6000_0003_0001_fingerprint_storage.md` - Fingerprint storage
+
+**MVP 4: Scanner Integration (Sprint 6000.0004)**
+- `SPRINT_6000_0004_0001_scanner_integration.md` - Scanner.Worker integration
+
+## Key Decisions
+
+| Decision | Rationale |
+|----------|-----------|
+| New `BinaryIndex` module | Binary vulnerability DB is distinct concern from Scanner |
+| Build-ID as primary key | Most deterministic identifier for ELF binaries |
+| `binaries` PostgreSQL schema | Aligns with existing per-module schema pattern |
+| Three-tier lookup | Assertions → Build-ID → Fingerprints for precision |
+| Patch-aware fix index | Handles distro backports correctly |
+
+## Module Structure
+
+```
+src/BinaryIndex/
+├── StellaOps.BinaryIndex.WebService/
+├── StellaOps.BinaryIndex.Worker/
+├── __Libraries/
+│   ├── StellaOps.BinaryIndex.Core/
+│   ├── StellaOps.BinaryIndex.Persistence/
+│   ├── StellaOps.BinaryIndex.Corpus/
+│   ├── StellaOps.BinaryIndex.Corpus.Debian/
+│   ├── StellaOps.BinaryIndex.FixIndex/
+│   └── StellaOps.BinaryIndex.Fingerprints/
+└── __Tests/
+```
+
+## Database Tables
+
+| Table | Purpose |
+|-------|---------|
+| `binaries.binary_identity` | Known binary identities |
+| `binaries.binary_package_map` | Binary → package mapping |
+| `binaries.vulnerable_buildids` | Vulnerable Build-IDs |
+| `binaries.cve_fix_index` | Patch-aware fix status |
+| `binaries.vulnerable_fingerprints` | Function fingerprints |
+| `binaries.fingerprint_matches` | Scan match results |
+
+## References
+
+- Original advisory: This folder
+- Architecture: `docs/modules/binaryindex/architecture.md`
+- Schema: `docs/db/schemas/binaries_schema_specification.md`
+- Sprints: `docs/implplan/SPRINT_6000_*.md`