re0-upgrade

1Keep one paperthin install per agent, current and loaded once, after you see and confirm the plan.
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3## Goal
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5Each agent runs paperthin from one route that stays current without the user remembering. Claude Code and Codex take the plugin route, which each host's own marketplace update keeps current; OpenCode and every other agent take the skills.sh route, which a daily per-user job keeps current. This skill does the part neither updater does: it moves an old skills.sh install onto the plugin route without leaving every skill loaded twice, removes the session-start notice older releases wired into agent configs, installs or checks the daily job where skills.sh stays, and brings a skills.sh install to the full current catalog, retiring renamed skills and adding the ones the user never installed. An integrity gate protects any locally edited copy before anything replaces or removes it.
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7It is **user-invoked** on purpose: it removes skill installs, edits agent configs and registers a scheduled job, so it runs only when the human asks.
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9## Deprecations
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11This section owns every rename and retirement, in release order; a future one appends its row here. A rename chain resolves to its final current name. A skill removed with no replacement carries `retired` (no backticks around the word in the table) in the Renamed-to column. The `ssot-check` row is user-confirmed history from before v0.2.0 that git cannot verify after a force-push; never invent its date or tag.
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