purpose-properties

# Purpose Properties Skill Retrofit and re-derive entry point for `purpose.yml#purpose_properties`. **For new projects this runs inside `/mycelium:start` Step 3b.** Use this skill when: - The project existed before **v0.120.0** and has no `purpose_properties` (the retrofit case — every project created before that release, since `/mycelium:start` Step 4 exits for already-initialized projects and never reaches the extraction). - `why`, `how` or `what` changed, so `derived_from_hash` no longer matches and **every stance below it is superseded** (the drift case — this is the one that matters most and the easiest to skip). - A property list exists but the user wants to revisit which properties are `binding`. Full contract: `${CLAUDE_PLUGIN_ROOT}/../../docs/purpose-stance.md`. ## Step 1: Read the current state and say which case this is Read `purpose.yml`. Then say plainly which of these you are in, because the three have different consequences and the user should not have to infer it: - **No `purpose_properties`** → retrofit. Nothing below has ever been checked against the purpose. - **Hash mismatch** → drift. Report it as *"your purpose changed after these were derived, so every `purpose_stance` below them was reasoned under a definition you have since changed."* This is the state that quietly invalidates work; name it in those terms. - **Hash matches** → nothing to do. Report the property count and stop. Do not re-derive for tidiness. ## Step 2: Attempt extracti...