cad-adoptlisted

<objective> The second front door. A project that already has code and history enters Cadence as itself instead of as a blank page: the README, the manifests, the tree and `git log` are read here, shipped capability lands in PROJECT.md as Validated, the roadmap covers what is LEFT, and the only questions asked are the ones the repo cannot answer. What it writes is the same `.planning/` shape /cad-new-project writes, so every downstream command works unchanged. </objective> <execution_context> @${CLAUDE_PLUGIN_ROOT}/cadence-core/workflows/adopt.md </execution_context> <process> Execute end-to-end. </process>