fix(research): keep the allowed-tools list; it pre-approves tools, it does not restrict them

6683da5 dropped allowed-tools on the premise that the list blocked
spawning. The repo's own docs describe the field as pre-approval, so the
list was never the cause and dropping it widened the tool surface for
nothing. Restore the list and keep the parallel fan-out in steps 4-5.

The spawn tool is not added: its name is sourced for Claude Code
(Agent) but not for Copilot or Codex, so spawns prompt rather than
being pre-approved.

ADR-0027 still asserts the dropped-list premise and is corrected
separately.

Refs #116

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EGHFJextYtVQseaHPDDhxB

plugins/bin/.apm/skills/research/SKILL.md

@@ -8,6 +8,15 @@ description: >-
 metadata:
   version: "1.1.0"
   category: research
+allowed-tools:
+  - Grep
+  - Glob
+  - Read
+  - Write
+  - WebSearch
+  - WebFetch
+  - mcp__context7__resolve-library-id
+  - mcp__context7__query-docs
 model: sonnet
 ---