merge: tick in-body checkboxes from a domain script

# Conflicts:
#	AGENTS.md

skills/issue/SKILL.md

@@ -36,6 +36,7 @@ All offline, all in `<skill-base-dir>/scripts/`.
 |---|---|
 | `issue_new.py --type T --title "…"` | create `tmp/issues/<slug>.md` from the type's template |
 | `issue_check.py [id…]` | validate against the canonical format; exit 1 on errors |
+| `issue_ac.py <id> [--check N\|TEXT]` | list the body's checkboxes; tick or untick one |
 | `issue_tree.py [id…]` | draw the dependency graph from `depends:` |
 | `issue_index.py` | rebuild `tmp/issues/INDEX.md` |
 | `issue.py` | the domain module the others import — not a command |
@@ -110,13 +111,48 @@ decision — `/tea:sync` — and does not change the file's status here.
 
 ## Editing an issue
 
-Edit the file. Change `state:` to close it, edit `labels:`, tick checkboxes in
-`## Acceptance criteria`, add ids to `depends:`. Re-run `issue_check.py`
-afterwards, and `issue_index.py` to refresh the table.
+Edit the file. Change `state:` to close it, edit `labels:`, add ids to
+`depends:`. Re-run `issue_check.py` afterwards, and `issue_index.py` to refresh
+the table. Checkboxes are the exception — use `issue_ac.py`, below.
 
 If the issue is synced (`origin: gitea`), your edit is local until you run
 `push.py --update` from `/tea:sync`. Nothing tracks that drift automatically.
 
+## Ticking checkboxes
+
+A checkbox is the one part of a body that is **state** and not prose, so it has
+a command of its own. Never rewrite a body just to tick a box: the rewrite
+re-flows lines and re-words sentences, and the issue's diff swells around a
+change that means one character.
+
+```bash
+python3 <skill-base-dir>/scripts/issue_ac.py wire-sqlc-appclick
+python3 <skill-base-dir>/scripts/issue_ac.py wire-sqlc-appclick --check 3
+python3 <skill-base-dir>/scripts/issue_ac.py wire-sqlc-appclick --check "регресс"
+python3 <skill-base-dir>/scripts/issue_ac.py wire-sqlc-appclick --uncheck 3
+```
+
+With no flag it prints the numbered list with each item's state, grouped by the
+heading the item sits under. `--check` / `--uncheck` take that number or a
+substring of the item's text (case-insensitive).
+
+- **Every checkbox in the body counts, not just `## Acceptance criteria`.** A
+  `type/feature` keeps its children as checkboxes under `## Issues`, and they
+  are numbered in the same list. The script is named after the section most
+  boxes live in, nothing more.
+- **A substring must match exactly one item.** Two matches is an error that
+  lists them; pick by number instead. It never guesses.
+- **Exactly one character of the file changes.** Metadata, wording, wrapping
+  and trailing whitespace all come back byte for byte, so `git diff` and the
+  tracker's diff show the tick and nothing else.
+- Examples inside a ``` fence are markup, not state — they are skipped.
+- `INDEX.md` gains a `progress` column (`3/7`, blank when the issue has no
+  boxes), recomputed from the body on every build and stored in no field.
+  `issue_ac.py` rebuilds the index after a successful tick.
+
+Getting the tick to the tracker is a separate step — `push.py --update` in
+`/tea:sync`.
+
 ## Writing a proper description
 
 Issues get filed on the run — "comments aren't pulled", "the guard broke".