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.

docs/modules/graph/AGENTS.md

@@ -10,7 +10,7 @@ Graph module (upcoming) will power graph-indexed queries for SBOM relationships,
 - [Task board](./TASKS.md)
 
 ## How to get started
-1. Open ../../implplan/SPRINTS.md and locate the stories referencing this module.
+1. Open sprint file `/docs/implplan/SPRINT_*.md` and locate the stories referencing this module.
 2. Review ./TASKS.md for local follow-ups and confirm status transitions (TODO → DOING → DONE/BLOCKED).
 3. Read the architecture and README for domain context before editing code or docs.
 4. Coordinate cross-module changes in the main /AGENTS.md description and through the sprint plan.
@@ -27,7 +27,7 @@ Graph module (upcoming) will power graph-indexed queries for SBOM relationships,
 - `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.