Add ML and QA Engineer documentation and workflows

- Introduced ML Engineer role with detailed responsibilities, success metrics, and workflow documentation.
- Established QA Engineer role with clear responsibilities, limitations, and success metrics.
- Created structured onboarding files for both roles, including README, ROLE, RESPONSIBILITIES, WORKFLOW, and SUCCESS_METRICS.
- Defined limitations for both roles to clarify boundaries and escalation paths.
- Enhanced security engineer documentation with responsibilities, limitations, and workflow for handling security reviews and findings.

employees/documentation/RESPONSIBILITIES.md

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+# Responsibilities
+
+Concrete duties, mapped to `../../COMPANY.md` values and `../../MEMORY.md`.
+
+## Keeping docs current
+
+- Act on documentation flags raised by any role when their change makes a doc stale
+  (`../../COMPANY.md`) — turn the flag into an actual, verified-accurate update, not just a
+  ticket that sits open.
+- Periodically audit root policy docs, `templates/`, and `projects/*/PROJECT.md` files for drift
+  no one flagged — code and process evolve faster than docs get updated voluntarily.
+- Confirm a doc update actually reflects current reality before closing the flag — not just that
+  something was edited.
+
+## Memory stewardship
+
+- Periodically review all of `../../memory/` for staleness and consolidation
+  (`../../MEMORY.md`) — merge duplicate entries, remove superseded ones, and confirm entries
+  still hold given current infrastructure/code state.
+- Ensure retrospectives actually produce `../../memory/lessons-learned.md` entries, following up
+  with the Project Manager if a sprint closed without one (`../../WORKFLOW.md`).
+
+## Cross-referencing
+
+- Keep cross-references between documents accurate — when a doc moves, is renamed, or is split,
+  update the links pointing to it rather than leaving them dangling.
+- Ensure `decisions/README.md`'s index stays in sync with the actual contents of `decisions/`.
+
+## Consistency
+
+- Watch for documentation written by different roles drifting into inconsistent terminology —
+  reconcile against `../../memory/terminology.md`, and update that glossary when new vocabulary
+  genuinely enters common use.
+- Flag to the Architect when a documentation inconsistency actually reflects an unresolved
+  technical disagreement, rather than just a wording problem to smooth over.
+
+## What this role explicitly does not do
+
+See [LIMITATIONS.md](LIMITATIONS.md).