feat(using-tasks): session_break marker [v1.2.0]

Add a session_break marker so a task author can mark a task's
completion as a natural session boundary. After the task closes 🟢,
before tasks_claim_next, an autonomous agent prints the verbatim
SESSION BOUNDARY line and stops instead of chaining the next task.
Absent -> behaviour unchanged.

- STATUS.md format: optional **Session break:** field + new
  "### session_break marker" subsection (type bool|string, examples).
- Task completion step 6: after close, before claim-next, check the
  closed task's session_break; print boundary line + stop if present.
- Rules bullet "Honour session_break".
- Wiki concept page concepts/using-tasks-session-break.md + index + log.

MINOR bump: new optional capability, no existing behaviour changed.
Closes [session-break-using-tasks].

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

skills/using-tasks/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: using-tasks
-version: 1.1.0
+version: 1.2.0
 description: >
   Policy skill for working with an existing `.tasks/` board (per-task files + STATUS.md).
   Use whenever the user is switching between tasks, resuming a paused task, starting a new
@@ -52,6 +52,7 @@ _Updated: YYYY-MM-DD_
 **Where I stopped:** one sentence — the exact thought or action interrupted
 **Next action:** one concrete step to resume immediately
 **Blocker:** (only if blocked) what is preventing progress
+**Session break:** (optional) `true` — or a hint string for the next track. Marks this task as a session boundary.
 **Branch:** git branch name
 
 ---
@@ -64,6 +65,18 @@ _Updated: YYYY-MM-DD_
 - 🟢 Done — completed, kept until merged
 - 🔵 Blocked — waiting on external input
 
+### `session_break` marker
+
+A task may carry a `session_break` marker — set by whoever defines the task (e.g. the delegating workshop) when its completion is a natural place to stop and start a fresh session. It signals an autonomous agent: *finish this task, then pause instead of immediately claiming the next one.*
+
+- **Type:** boolean or string.
+  - `session_break: true` — pause after close; the next track is "see STATUS.md".
+  - `session_break: "<hint>"` — pause after close; `<hint>` names the recommended next track.
+- **Where it lives:** in the task's frontmatter when delivered via the task system (`session_break: true` / `session_break: "<hint>"`); mirrored on the local board as the optional `**Session break:**` field in the task's STATUS.md block.
+- **Absent →** behaviour is unchanged: close the task and continue as usual.
+
+The check is enforced in the **Task completion** flow below (after close, before claiming the next task).
+
 ---
 
 ## Per-task file format (`<task-slug>.md`)
@@ -133,6 +146,13 @@ Temporary hypotheses, links, names of people to consult.
 3. Set status to 🟢 in STATUS.md.
 4. Append final summary line to Decisions log.
 5. Remind user to delete the branch after merge.
+6. **Session-break check (after close, before claiming the next task).** Once the task is 🟢 and committed — and **before** any `tasks_claim_next` or starting the next task — read the closed task's `session_break` marker (its frontmatter `session_break`, or the `**Session break:**` field in its STATUS.md block). If present:
+   - Print this line **verbatim**, substituting the closed task's slug for `[slug]` and the marker's string value for `[value | "см. STATUS.md"]` (use the literal `см. STATUS.md` when the marker is just `true`):
+
+     `🔚 SESSION BOUNDARY — [slug] закрыта. Рекомендую завершить текущую сессию. Следующий трек: [value | "см. STATUS.md"]`
+
+   - **Stop.** Do not claim or start the next task.
+   - If the marker is absent → behaviour is unchanged: proceed to claim / start the next task as usual.
 
 ### Post-commit task closure prompt
 
@@ -171,4 +191,5 @@ Pair: `using-projects-meta` declares local-first for **reads**; this rule extend
 - **Always confirm orientation at session start** — state understanding before acting.
 - **One active task at a time** — only one 🔴 in STATUS.md.
 - **Never close a task without a coverage check** — see "### Task completion" step 1. Acceptance criteria with no evidence → ask, don't auto-close.
+- **Honour `session_break`** — a closed task carrying a `session_break` marker means stop after close; never chain into `tasks_claim_next`. See "### Task completion" step 6.
 - **Local-first recommendations** — cwd-project board comes first; cross-project urgents are at most one footnote line.