chore: remove outdated documentation and prep notes

- Deleted several draft and prep documents related to benchmarks, authority DPoP & mTLS implementation, Java analyzer observation, link-not-merge determinism tests, replay operations, and crypto provider registry.
- Updated the merge semver playbook to reflect current database schema usage.
- Cleaned up the technical development README to remove references to obsolete documents and streamline guidance for contributors.

docs/dev/merge_semver_playbook.md

@@ -69,7 +69,7 @@ db.advisories.aggregate([
 ]);
 ```
 
-Pair this query with the indexes listed in [Normalized Versions Query Guide](mongo_indices.md).
+**Note:** The above MongoDB query syntax is for reference only. The current system uses PostgreSQL. See `docs/db/SPECIFICATION.md` for current database schema.
 
 ## 5. Recommended indexes
 
@@ -98,7 +98,7 @@ Follow the operational checklist in `docs/modules/devops/migrations/semver-style
 - [ ] Capture merge decisions via `decisionReason`.
 - [ ] Confirm integration tests include fixtures with normalized rules and SemVer styles.
 
-For deeper query examples and maintenance tasks, continue with [Normalized Versions Query Guide](mongo_indices.md).
+For current database schema and query patterns, see `docs/db/SPECIFICATION.md`.
 
 ## 8. Storage projection reference