fix(sdk): task 10 review round 1 — name the ws.libs-only library skip, don't drop it

builtPluginsFromOutcomes now returns unpublishableLibraries for any build outcome
that matched no ws.plugins entry — a ws.libs-only library (kind:"library" but
outside s2script.workspace.plugins), previously dropped by a `continue` whose
comment claimed the branch was unreachable. It is a live path: buildWorkspace
builds every declared library ahead of the plugin loop and folds both into one
outcomes array. commands/deploy.ts now prints an explicit skip line for each,
right under the plan, naming the remedy (`s2s deploy <relDir>`). computePlan/
uploadPlan are untouched — nothing about what actually gets published changed.