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/README.md

@@ -58,6 +58,9 @@ Requires Python ≥ 3.10. No third-party packages — the server is pure stdlib.
 | `sleep_run` | full cycle; stages a proposal for review |
 | `sleep_adopt` | apply the staged proposal; syncs skill to the workspace |
 | `sleep_harvest` | debug: list the recurring tasks mined |
+| `sleep_schedule` | install a nightly cron entry (`--hour` / `--minute`) |
+| `sleep_unschedule` | remove the nightly cron entry |
 
 Default backend is `mock` (no API spend); `--backend claude|codex` uses your own
-budget. Same engine as the other plugins — all call `python -m skillopt_sleep`.
+budget. Same engine and `sleep_*` interface as the other plugins — all call
+`python -m skillopt_sleep`.