define-use-caselisted

# Define Use Case Entry point for adding a single use case to a target project. The skill is deterministic: one use case per invocation, no batching. Run it again to add another. ## Preconditions - Must run from the **root Claude Code session** so the follow-up can hand off to `develop` without nested spawning. - The target folder must already contain a `PROJECT_BRIEF.md`. If it does not, stop and point the user at `project-builder` — use cases without a project context are not useful. ## Step 1 — Resolve folders 1. Run `pwd` via Bash to get `SESSION_DIR`. 2. Ask the user for the target project folder (`TARGET_DIR`) as an absolute path. Resolve relative paths with `cd <path> && pwd` and confirm. 3. Refuse and re-ask if `TARGET_DIR` equals, contains, or is contained by `SESSION_DIR` (path-segment comparison — `/foo/bar` is not a prefix of `/foo/barbaz`). 4. Confirm `<TARGET_DIR>/PROJECT_BRIEF.md` exists. If it does not, stop and tell the user to run `project-builder` first. ## Step 2 — Load project context Read `<TARGET_DIR>/PROJECT_BRIEF.md`. You need this as background so the formalized use case stays consistent with the project's stack, architecture, and stated non-goals. The only writes this skill performs on the brief are scoped to the `use_cases` frontmatter block (path bookkeeping) and a single `## Use Cases` prose paragraph pointing at the ledger — both handled in Step 6b. No other section, and no other frontmatter field, may be touched. ## Step 2b — Acquire t