devin plugin: full schema/tool parity with plugins/copilot

Mirror the copilot MCP server: same rich _TOOL_SCHEMA (source, model,
tasks_file, target_skill_path, max_sessions, max_tasks, lookback_hours,
auto_adopt, json, edit_budget, hour, minute) and generic flag forwarding, plus
sleep_schedule / sleep_unschedule. Devin specifics retained: the ATIF-v1.7
harvest step (run before data-reading actions, engine pointed at it via
--claude-home, default --source claude) and post-adopt sync into .devin/skills/.
Tests + README + rules snippet updated for the 7-tool interface.

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

plugins/devin/devin-rules.snippet.md

@@ -8,6 +8,7 @@ server. Use these tools to improve your long-term skills over time:
 - **`sleep_run`** — run a full cycle; stages a proposal for review
 - **`sleep_adopt`** — apply the staged proposal to `.devin/skills/skillopt-sleep-learned/SKILL.md`
 - **`sleep_harvest`** — debug: list the recurring tasks mined from recent sessions
+- **`sleep_schedule`** / **`sleep_unschedule`** — install/remove a nightly cron run
 
 When a user asks about the sleep cycle, skill evolution, or improving your
 long-term memory, prefer calling these tools over explaining the concept.