Add sdp-release-process-run skill: operational layer for executing
doc/ReleaseProcessOverview.md step by step.
Per the user, while actually executing the SDP 2026.1 release:
captures the "one step, then stop for confirmation" human-in-the-
loop accountability pattern as a standing practice, plus the
AI-specific shell-environment know-how needed to follow that doc
correctly (non-persistent shell state between tool calls, which
workspace/stream for which step, when generated docs are isolated
per-stream, the PDF-regeneration-only-at-release-time policy, and
the preview-before-merge/copy practice).
Deliberately doesn't duplicate ReleaseProcessOverview.md's own step
content -- that doc is the source of truth and can change (it did,
mid-release, twice, the same day this skill was written).