ref(mcp): neutralize dev-shaped vocabulary in _INSTRUCTIONS + add write-mandate (B9/A4)

The MCP instructions are domain-neutral except a thin layer of dev vocabulary
and one project-specific paragraph (B10 audit, task 812). Make the data store's
own instructions serve any domain, and add the missing positive write-mandate.

B9 (neutralize):
- 'before writing code' -> 'before you dive in'
- Note examples 'dev-logs' -> 'logs of what happened'
- record trigger 'a merge, a shipped feature, a finished plan' + 'dev-log note'
  -> 'finishing a task, or hitting/discovering a problem that changes direction'
  (folds in B8: log pivots, not just wins; mirrors the static-tier wording)
- recall examples 'ticket/dev-log' -> 'task/prior note' (server + SKILL.md)
- 'Engineering and workflow rules' -> 'Workflow and standards rules'
- slim the 'developing Scribe itself' ACL paragraph to a neutral one-liner
  (project-specific specifics already live in rules #47/#78)

A4 (write-mandate): state up front that Scribe is the system of record — record
work here, recall before acting, don't keep project work in local files.

Refs plan 812 (B9, A4, B8-trigger); B10 audit work-log.

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

plugin/skills/using-scribe/SKILL.md

@@ -51,7 +51,7 @@ Two constraints on *how* that's achieved:
 
 1. **Recall before acting.** Before answering a question about the operator's
    work, or starting a task, `search` Scribe (and `list_tasks` / `list_notes`)
-   for prior art — an existing ticket, decision, or dev-log — instead of
+   for related prior work — an existing task, decision, or note — instead of
    re-deriving it or opening a duplicate. When a project is in scope, pass its
    `project_id` so results stay scoped.