fix: save research silently via background Bash, not Write tool

The Write tool displays "Wrote N lines..." after the invitation,
ruining the end-of-run experience. Now saves via background Bash
with a subtle 📎 footer line in the invitation text.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SKILL.md

@@ -500,25 +500,23 @@ For `/last30days war in Iran` (NEWS):
 
 ## Save Research to Documents
 
-After displaying the invitation, save the complete research briefing to the user's Documents folder. This happens automatically on every run.
+After displaying the invitation, save the complete research briefing to `~/Documents/Last30Days/`. This happens automatically on every run.
 
-1. **Create the directory** (if it doesn't exist):
-   ```bash
-   mkdir -p ~/Documents/Last30Days
-   ```
+**Generate the filename** from TOPIC:
+- Lowercase, replace spaces/special chars with hyphens, remove consecutive hyphens, trim to 60 chars
+- Example: "Claude Code Best Practices" → `claude-code-best-practices.md`
+- If file already exists, append today's date: `{slug}-YYYY-MM-DD.md`
 
-2. **Generate the filename** from TOPIC:
-   - Lowercase the topic
-   - Replace spaces and special characters with hyphens
-   - Remove consecutive hyphens
-   - Trim to 60 characters max
-   - Example: "Claude Code Best Practices" -> `claude-code-best-practices`
+**End your invitation with a single `📎` footer line:**
 
-3. **Check for duplicates**: If `~/Documents/Last30Days/{slug}.md` already exists, append today's date: `{slug}-YYYY-MM-DD.md`
+```
+📎 ~/Documents/Last30Days/{slug}.md
+```
 
-4. **Use the Write tool** to save to `~/Documents/Last30Days/{slug}.md` with this exact structure:
+**Then immediately save using a background Bash command** (`run_in_background: true`):
 
-```markdown
+```bash
+mkdir -p ~/Documents/Last30Days && cat > ~/Documents/Last30Days/{slug}.md << 'RESEARCH_EOF'
 # {TOPIC}
 
 > Researched {date} | Query type: {QUERY_TYPE} | Target tool: {TARGET_TOOL or "general"}
@@ -537,15 +535,20 @@ After displaying the invitation, save the complete research briefing to the user
 
 ---
 *Generated by [last30days](https://github.com/mvanhorn/last30days-skill) v2.9.1*
+RESEARCH_EOF
 ```
 
-5. **Confirm briefly** after saving: `Saved to ~/Documents/Last30Days/{slug}.md`
+**CRITICAL RULES:**
+1. NEVER use the `Write` tool — it displays "Wrote N lines..." which ruins the experience
+2. ALWAYS use `run_in_background: true` so the Bash call is nearly invisible
+3. The `📎` line is part of your text message, not a separate tool call
+4. The invitation + `📎` line must be the LAST visible thing on screen
 
 ---
 
 ## WAIT FOR USER'S RESPONSE
 
-After showing the stats summary with your invitation, **STOP and wait** for the user to respond.
+**STOP and wait** for the user to respond.
 
 ---