New gstack skill that hands a task between agentic harnesses (Codex,
Hermes, Antigravity, Claude Code) via one canonical [handoff] block
written to a Plane comment, /context-save notes, and a gbrain page.
Release with /handoff, claim with /handoff take <TASK-ID>. Pointer-based
(refs + targeted gbrain lookups) so resuming does not re-ingest a
transcript; failed: field is mandatory to avoid repeated dead ends.
sdoan99