Update AGENTS.md files across multiple modules to standardize task status update instructions and introduce a new document for Secret Leak Detection operations.

- Modified task status update instructions in AGENTS.md files to refer to corresponding sprint files as `/docs/implplan/SPRINT_*.md` instead of `docs/implplan/SPRINTS.md`.
- Added a comprehensive document for Secret Leak Detection operations detailing scope, prerequisites, rule bundle lifecycle, enabling the analyzer, policy patterns, observability, troubleshooting, and references.

src/Findings/StellaOps.Findings.Ledger/AGENTS.md

@@ -17,7 +17,7 @@ Operate the append-only Findings Ledger and projection pipeline powering the Vul
 5. **Auditability** – Provide verifiable hashes, Merkle roots, and replay tooling for auditors.
 
 ## Collaboration
-- Keep `src/Findings/StellaOps.Findings.Ledger/TASKS.md`, `../../docs/implplan/SPRINTS.md` synchronized.
+- Keep `src/Findings/StellaOps.Findings.Ledger/TASKS.md`, `/docs/implplan/SPRINT_*.md` synchronized.
 - Publish schema docs, migrators, and replay scripts; coordinate with Vuln Explorer API on projection contracts.
 - Notify DevOps/Docs when Merkle root anchoring cadence or format changes.
 
@@ -37,7 +37,7 @@ Operate the append-only Findings Ledger and projection pipeline powering the Vul
 - `docs/modules/platform/architecture-overview.md`
 
 ## Working Agreement
-- 1. Update task status to `DOING`/`DONE` in both `docs/implplan/SPRINTS.md` and the local `TASKS.md` when you start or finish work.
+- 1. Update task status to `DOING`/`DONE` in both correspoding sprint file `/docs/implplan/SPRINT_*.md` and the local `TASKS.md` when you start or finish work.
 - 2. Review this charter and the Required Reading documents before coding; confirm prerequisites are met.
 - 3. Keep changes deterministic (stable ordering, timestamps, hashes) and align with offline/air-gap expectations.
 - 4. Coordinate doc updates, tests, and cross-guild communication whenever contracts or workflows change.