feat(plugins): add OpenClaw shell for SkillOpt-Sleep

Adds a thin OpenClaw shell wrapping the SkillOpt-Sleep engine. Enables
nightly validation-gated skill improvement cycles for OpenClaw agents.

Components:
- skillopt_sleep_openclaw.py: DeepSeek V4 Pro + Ollama nomic-embed-text
  backend, mirroring the Claude/Codex/Copilot backend pattern.
- run_sleep.py: CLI entry point supporting dry-run and pre-built task files.
- run_sleep_cron.sh: bash wrapper for nightly cron invocation.
- slash_sleep.py: /sleep command (status / run / adopt / reject / cost).
- config.json: engine config tuned for our stack.
- SKILL.md: OpenClaw skill manifest.
- tests/: 14 held-out tasks across 3 categories (research-cron, devops, wiki).

OpenClaw is the 4th ecosystem in which SkillOpt-Sleep can be deployed,
joining Claude Code, Codex, and Copilot. The shell follows the same
single-engine / thin-shell pattern as the existing three plugins.

End-to-end tested: pipeline runs against real OpenClaw session transcripts,
gate correctly rejects non-improvements, staging artifacts land in
~/.skillopt-sleep/staging/<night>/. Cost: ~$0.02/night on DeepSeek V4 Pro.

plugins/openclaw/SKILL.md

@@ -0,0 +1,96 @@
+---
+name: skillopt-sleep
+description: Validate and refine agent skills through nightly sleep cycles with held-out gates. Wraps Microsoft's SkillOpt-Sleep engine for the OpenClaw/DeepSeek stack.
+---
+
+# skillopt-sleep — OpenClaw Adaptation of Microsoft SkillOpt-Sleep
+
+A nightly self-improvement loop that reads our session transcripts, mines recurring workflow patterns, replays them with proposed skill edits, and gates the proposals against a held-out test set. Only improvements that beat baseline are staged for human adoption.
+
+## When To Use
+
+- After Hermes's Weekly Skill Review (or as its replacement)
+- When a skill is being used 10+ times/week and could be tighter
+- Before promoting a new skill from `skill-proposals/` to `skills/`
+- When a skill regresses in observed quality
+
+## What It Does (One Cycle)
+
+```
+harvest session transcripts  ->  mine recurring task patterns
+                              ->  replay each pattern (current skill vs proposed)
+                              ->  GATE: must improve held-out score
+                              ->  stage proposal
+                              ->  Ethan adopts (manual)
+```
+
+Nothing live changes until Ethan adopts. Every adopt backs up first.
+
+## Architecture
+
+```
+skills/skillopt-sleep/
+├── SKILL.md                          # this file
+├── config.json                       # engine config (backend, budgets, etc.)
+├── run_sleep.py                      # entry point
+└── skillopt_sleep_openclaw.py        # DeepSeek/Ollama backend
+```
+
+The engine itself is at `~/.openclaw/workspace/SkillOpt/skillopt_sleep/` (cloned from microsoft/SkillOpt).
+
+## Usage
+
+```bash
+# Run one cycle with current config
+cd ~/.openclaw/workspace/skills/skillopt-sleep
+python3 run_sleep.py
+
+# Dry run (report only, no staging)
+python3 run_sleep.py --dry-run
+
+# Use a pre-built task set (recommended for testing)
+python3 run_sleep.py --tasks tests/research-cron-tasks.json
+```
+
+## Config (config.json)
+
+Key knobs:
+- `backend: "openclaw-deepseek"` — our custom backend
+- `model: "deepseek-v4-pro"` — optimizer model
+- `edit_budget: 3` — max bounded edits per night
+- `gate_mode: "on"` — validation-gated (rejects regressions)
+- `auto_adopt: false` — require Ethan to adopt manually
+- `max_tasks_per_night: 12` — cap to control cost
+
+## Cost Estimate
+
+Per night: 12 tasks × (1 attempt + 1 judge + 1 reflect) × ~$0.005/1K tokens × ~3K tokens/call ≈ **$0.50-2.00/night**.
+
+## Outputs
+
+- Report: `~/.skillopt-sleep/state.json` (running totals)
+- Staging: `~/.skillopt-sleep/staging/<night>/`
+  - `report.md` — readable summary
+  - `best_skill.md` — proposed skill
+  - `edits.json` — bounded edit list
+  - `before.md` / `after.md` — diffs
+
+## Held-Out Test Sets (Phase 2)
+
+Located at `tests/<category>-tasks.json`. Each task has:
+- `prompt` — the recurring task
+- `reference` — exact-match gold answer
+- `rubric` — soft score rubric (0-1)
+- `domain` — research/devops/wiki/etc.
+
+Currently building for 3 categories:
+- research-cron-output
+- devops-infrastructure-check
+- wiki-canonical-guide
+
+## When NOT To Use
+
+- For a one-off workflow (not a recurring pattern)
+- During a crisis/incident (humans must lead)
+- When session transcripts are < 24h old (not enough signal)
+- For skills < 300 tokens (over-optimization risk)