chore: refine platform policy and memory SKILL docs

nanobot/skills/memory/SKILL.md

@@ -9,15 +9,20 @@ always: true
 ## Structure
 
 - `memory/MEMORY.md` — Long-term facts (preferences, project context, relationships). Always loaded into your context.
-- `memory/HISTORY.md` — Append-only event log. NOT loaded into context. Search it with grep. Each entry starts with [YYYY-MM-DD HH:MM].
+- `memory/HISTORY.md` — Append-only event log. NOT loaded into context. Search it with grep-style tools or in-memory filters. Each entry starts with [YYYY-MM-DD HH:MM].
 
 ## Search Past Events
 
-```bash
-grep -i "keyword" memory/HISTORY.md
-```
+**Recommended approach (cross-platform):**
+- Use `read_file` to read `memory/HISTORY.md`, then search in-memory
+- This is the most reliable and portable method on all platforms
 
-Use the `exec` tool to run grep. Combine patterns: `grep -iE "meeting|deadline" memory/HISTORY.md`
+**Alternative (if you need command-line search):**
+- **Linux/macOS:** `grep -i "keyword" memory/HISTORY.md`
+- **Windows:** `findstr /i "keyword" memory\HISTORY.md`
+- **Python (cross-platform):** `python -c "import re; content=open('memory/HISTORY.md', encoding='utf-8').read(); print('\n'.join([l for l in content.split('\n') if 'keyword' in l.lower()][-20:]))"`
+
+Use the `exec` tool to run these commands. For complex searches, prefer `read_file` + in-memory filtering.
 
 ## When to Update MEMORY.md