feat(delegate-task): session_break authoring field [v0.2.2]

Add the authoring side of the `session_break` marker whose consumer
side shipped in using-tasks v1.2.0. At delegation time the author can
now mark a task so that, after it closes, an autonomous runner pauses
instead of chaining the next task.

- Pre-flight gate 5->6 questions: new Q (item 5, after notify) —
  "Session-break после этой задачи? (domain-switch / milestone /
  heavy infra)". Yes -> set session_break in body; no -> omit
  (default unchanged).
- Template trailer gains optional `[**session_break:** true |
  "<hint>"]` with inline comment (same lowercase frontmatter key
  using-tasks reads).
- Usage-guidance block: three set-it cases + tie to using-tasks
  Task-completion step 6 / SESSION BOUNDARY line.
- What-NOT-to-do bullet: don't set it routinely (real-boundary
  marker, not a default).
- Wiki concept page concepts/delegate-task-session-break.md
  (links using-tasks-session-break) + index + log.

PATCH bump: additive optional field + one pre-flight question, no
existing behaviour changed. Markdown policy artifact — no test
surface (TDD N/A). Closes [session-break-delegate-task].

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

.wiki/index.md

@@ -42,6 +42,7 @@ Catalog of all wiki pages. One line per page, organized by type. Updated on ever
 - [interns-grep-audit-design](concepts/interns-grep-audit-design.md) — interns-grep-audit-design
 - [session-handoff-skill-design.md](concepts/session-handoff-skill-design.md) — design rationale for the `session-handoff` skill (sliding overwrite into `.tasks/NEXT_SESSION.md`, phrase whitelist + substantive-commit heuristic, optional PostToolUse hook for harness-side determinism, orient+ask default, project scope, cluster 7/7 closure)
 - [using-tasks-session-break.md](concepts/using-tasks-session-break.md) — `using-tasks` v1.2.0 `session_break` marker: task-author-set boolean/string flag; after a task closes 🟢, before `tasks_claim_next`, an autonomous agent prints the verbatim SESSION BOUNDARY line and stops instead of chaining the next task. Absent → unchanged
+- [delegate-task-session-break.md](concepts/delegate-task-session-break.md) — `delegate-task` v0.2.2 — authoring side of the `session_break` marker (consumer = [[using-tasks-session-break]]): pre-flight Q6 + optional template field `session_break: true | "<hint>"`; three set-it cases (domain-switch / milestone / heavy infra); not a default
 - [delegate-task-negative-trigger-fp.md](concepts/delegate-task-negative-trigger-fp.md) — `delegate-task` v0.2.1 FP fix: «создать задачу себе» stem-matched the «создать задачу на агента» positive trigger; abstract "does NOT apply when doing the work yourself" carve-out loses to literal stem-match under the 1%-rule → made the negative literal + routed (→ using-tasks). Verified pos 5/5, neg 4/5 (was 0/5)
 
 ## Packages