docs: check dependents per-branch with --base, not a capped sweep

Review comment on the verify step: dumping every open PR under
--limit 1000 wastes agent context and re-truncates past 1000. Ask the
exact question server-side instead: gh pr list --state open
--base <branch> --json number --jq length, whose output is a single
count that is exact at any number of open PRs. Skill, checklist, and
the cookbook dependent-check line all use the per-branch form.

.agents/skills/dsh-merging-stacked-prs/SKILL.md

@@ -32,13 +32,13 @@ Each retarget step merges the freshly-updated master back into the dependent bra
 
 ## Verify before deleting anything
 
-Before *any* branch delete, confirm nothing still depends on it:
+Before deleting a branch, ask GitHub directly whether any open PR still bases on it:
 
 ```sh
-gh pr list --state open --limit 1000 --json number,baseRefName
+gh pr list --state open --base <branch> --json number --jq length
 ```
 
-The explicit `--limit` matters: without it the list is paginated, and a dependent past the first page would make deletion look safe when it is not. If any open PR's `baseRefName` is a branch you're about to delete, **do not delete it** — that PR will auto-close. Default to merging without `--delete-branch` throughout, and do the deletions as a separate final pass once the list shows no open dependents.
+Anything other than `0` means deleting `<branch>` auto-closes that many open PRs — do not delete it. The `--base` filter is applied server-side, so the answer is exact no matter how many PRs are open, and the output is a single number. Default to merging without `--delete-branch` throughout, and do the deletions as a separate final pass once every branch you're about to delete reports `0`.
 
 ## Longer chains
 
@@ -48,5 +48,5 @@ The pattern extends to any depth. For `A ← B ← C ← D ← …`, walk the st
 
 - [ ] Merge bottom PR first, `--merge`, no `--delete-branch`; wait until `gh pr view <n> --json state` shows `MERGED`.
 - [ ] For each dependent: `gh pr edit <n> --base master` → fetch and merge `origin/master` into the branch (resolve conflicts there, push) → `gh pr merge <n> --merge`, no `--delete-branch`; again wait for `MERGED`.
-- [ ] Run `gh pr list --state open --limit 1000 --json number,baseRefName` to confirm no open dependents remain.
+- [ ] Before each branch delete: `gh pr list --state open --base <branch> --json number --jq length` prints `0`.
 - [ ] Delete all branches (local + remote) only as a final pass.

docs/cookbook/responding-to-pr-review-on-a-stack.md

@@ -15,7 +15,7 @@ A wave of review comments lands across several PRs in a dependent stack (`A ←
 2. Map each accepted finding to its originating PR, fix it there, then merge down the chain in order.
 3. Delegated fixes are trust-but-verify: a sub-agent's report describes intent, not necessarily what landed. Re-run the gates yourself on the actual tree, and for a regression guard, prove it FAILS on the unfixed code (introduce the regression, watch red, revert) — a guard that passes both ways guards nothing. A sub-agent that reframes a problem as already-handled is a signal to dig in personally.
 4. Reply in the review thread (`gh api repos/{owner}/{repo}/pulls/{pr}/comments/{id}/replies`), not as a top-level comment, stating the fix and the commit that carries it.
-5. Before merging the stack, check dependents: deleting a PR's base branch auto-closes the dependent PR — `gh pr list --state open --limit 1000 --json number,baseRefName` first (the explicit `--limit` defeats pagination), and merge without `--delete-branch` where a child still bases on the branch. The full landing procedure is the [dsh-merging-stacked-prs](../../.agents/skills/dsh-merging-stacked-prs/SKILL.md) skill.
+5. Before merging the stack, check dependents: deleting a PR's base branch auto-closes the dependent PR — check each branch with `gh pr list --state open --base <branch> --json number --jq length` (non-zero = open dependents), and merge without `--delete-branch` where a child still bases on the branch. The full landing procedure is the [dsh-merging-stacked-prs](../../.agents/skills/dsh-merging-stacked-prs/SKILL.md) skill.
 
 ## Verify