feat(mcp): S5 — issue-kind guidance across all instruction surfaces

Plan #825 (T2 — Issues task_kind) shipped S1–S4 but its S5 docs slice
never landed, so every behavioral surface the plugin pushes to the agent
still described the pre-kind convention ("tag `issue`" on a create_note).
Result: agents fixed bugs without reaching for kind=issue and dumped the
work as logs on unrelated open tasks.

- _INSTRUCTIONS: rewrite the "record a problem" bullet to
  create_task(kind="issue") with symptom→cause→fix + arose_from_id /
  system_ids, and an explicit "not a work-log on an unrelated task"; add
  Issue + System to the hierarchy section.
- skills/systematic-debugging, verification: drop "tag `issue`" /
  create_note-issue, point at create_task(kind="issue").
- skills/using-scribe: add issues/systems to the entity list + reflex #6.
- hooks/scribe_static_context: fix → its own issue on the keyless floor.

Instance-agnostic, prose-only; no schema or tool-behavior change.
Pairs with always-on rule #118. Issue: #855.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugin/hooks/scribe_static_context.md

@@ -20,7 +20,9 @@ for the operator's work, and as your own working memory across sessions.
   `add_task_log`. Always log when you **complete a task** and when you **hit or
   discover a problem** — so changes of direction are captured, not just
   successes. Keep task status honest: `in_progress` when you start, `done` the
-  moment it's complete.
+  moment it's complete. When you **fix** something — even in passing — record it
+  as its own issue (`create_task(kind="issue")`), not as a work-log line on an
+  unrelated open task.
 - Do **not** keep the operator's rules, plans, or project notes in local
   memory / CLAUDE.md in parallel with Scribe — Scribe holds the single copy.
 - **Compact at clean seams** — because you record as you go, a context