chore: overnight plan 2026-03-04 + /overnight command

- Rewrote loop/plan.md with 34 checkbox tasks across 8 phases
- Updated loop/prompt.md for new overnight scope
- Added .claude/commands/overnight.md skill
- Self-destructing dev SW from previous session

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

.claude/commands/overnight.md

@@ -0,0 +1,11 @@
+Prepare and launch the overnight automation loop. Do ALL of these steps in order:
+
+1. Commit all uncommitted changes on the current branch with message: `chore: pre-overnight snapshot`
+2. Push the current branch to origin
+3. Check if branch `overnight/$DATE` exists (where $DATE is today's date YYYY-MM-DD). If it does, check it out. If not, run `./loop/prepare.sh` to create it.
+4. Commit `loop/plan.md` and `loop/prompt.md` on the overnight branch: `chore: overnight plan $DATE`
+5. Push the overnight branch: `git push -u origin overnight/$DATE`
+6. Start the loop in the background: run `caffeinate -i ./loop/loop.sh` using Bash with `run_in_background: true`
+7. Report: branch name, task count from plan.md, and confirm the loop is running
+
+If any step fails, stop and report the error — do not continue.