fix(finishing): name the actual files in the refusal prompt

`git status --porcelain` collapses a wholly-untracked directory to a single
`?? docs/` line. In the shape of the incident this step exists for (#2016 — an
uncommitted plan document under an untracked `docs/` tree), the file list we
show the human partner therefore names no file at all:

    $ git -C "$WORKTREE_PATH" status --porcelain
    ?? docs/
    $ git -C "$WORKTREE_PATH" status --porcelain -uall
    ?? docs/superpowers/plans/2026-08-04-csv-export-rollout.md

Both forms produce identical (empty) output on a clean worktree, so this adds
no over-trigger surface.

Found while running this PR's behavioral micro-tests. Every treatment agent
dug past `?? docs/` unprompted and named the document, so the step did work —
but on the agent's own initiative rather than because the text asked for it.
That initiative is not reliable one tier down: Claude Haiku 4.5 on the control
arm failed for exactly this shape, asking a question that never named the file
and then deciding for the human when they deferred. Nothing in the prior
wording stopped a treatment agent from relaying `?? docs/` verbatim and
satisfying the letter of the instruction.

Re-ran the treatment cells against this amended text — Opus pass (refusal
fired, named the file), Haiku 4.5 pass (named the file) — no regression.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

skills/finishing-a-development-branch/SKILL.md

@@ -174,6 +174,29 @@ git worktree remove "$WORKTREE_PATH"
 git worktree prune  # Self-healing: clean up any stale registrations
 ```
 
+**If removal is refused** (`contains modified or untracked files`): the
+worktree holds files that exist nowhere else — uncommitted plans, notes,
+or scratch work. Never `--force` on your own initiative. Show your human
+partner what is at stake and ask:
+
+```bash
+git -C "$WORKTREE_PATH" status --porcelain -uall
+```
+
+```
+Worktree removal refused — these files were never committed:
+
+<file list>
+
+1. Commit them to <branch> before cleanup
+2. Move them into <main repo root>
+3. Delete them (unrecoverable)
+
+Which?
+```
+
+Carry out the choice, then remove the worktree.
+
 **Otherwise:** The host environment owns this workspace — leave it in
 place. If your platform provides a workspace-exit tool, use it.
 
@@ -196,6 +219,7 @@ place. If your platform provides a workspace-exit tool, use it.
 | "'Yeah, get rid of it' counts as confirmation" | Only the typed word `discard` authorizes deletion. |
 | "The PR is up, so the worktree is clutter now" | PR feedback gets fixed in that worktree. It stays until the work lands. |
 | "This other worktree looks stale — I'll clean it too" | Clean up only worktrees under `.worktrees/` or `worktrees/`. Everything else belongs to the host. |
+| "Removal refused — `--force` is just finishing the cleanup" | The refusal means files exist only in that worktree. `--force` destroys them permanently. Show your human partner and ask. |
 | "The merged-result failure is probably flaky" | A failing merged result stops everything. Branch and worktree stay put while you investigate. |
 | "The base branch is obviously main" | Confirm the fork point or ask. Merging into the wrong base is expensive to undo. |
 | "The push was rejected — force-push will fix it" | A rejected push means the remote moved. Investigate; force-push only on your human partner's explicit request. |