feat(schema): add sibling-command disambiguation to avoid_when
Add skills/mono/schema-hints/sibling-disambiguation.json: for each multi-segment
command sub-group (aitable view update, sheet range, chat message, ...), append
explicit cross-referencing avoid_when entries pointing agents to the correct
sibling command. Regenerate embedded agent metadata + catalog: 395/504 tools now
carry sibling disambiguation, improving tool-selection beyond template-only
avoid_when. drift/catalog gates and go test ./internal/cli pass.