plugin-upgrade 2

Plugin-author upgrade skill for DeepSeek Harness: the merged version-locked 0.1.3-alpha.1 -> 0.1.5-rc.1 corridor card plus a zero-dependency seam scanner over one 20-seam catalog — leg A (V3 session format, assistant/message.stream, SessionHandleReadResul

Plugin-author upgrade skill for DeepSeek Harness: a version-locked 0.1.5-alpha.1 -> 0.1.5-rc.1 corridor card plus a zero-dependency seam scanner (the removed bare `conversation` client slot, the sidebar textpreview -> documentpreview package rename, the n