chore: gitignore screenshots, scheduled-tasks lock, playwright cache

Working tree was accumulating debris across sessions:
- Headless-Chrome / visual-companion screenshots in repo root (dozens
  of throwaway PNGs from design iteration)
- .claude/scheduled_tasks.lock from autonomous-loop runs
- .playwright-mcp/ cache from the Playwright MCP server

Adds explicit ignores so these stay local. Intentionally archived
screenshots belong under docs/; the /*.png pattern only catches
root-level debris.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -1,4 +1,16 @@
 .superpowers/
 .mcp.json
 .claude/settings.local.json
+.claude/scheduled_tasks.lock
 ezscale-discovery-*/
+
+# Docker dev env
+.env.docker
+
+# Playwright MCP cache + per-session debris
+.playwright-mcp/
+
+# Loose screenshots from headless Chrome / visual companion sessions.
+# Intentionally archived screenshots belong under docs/; root-level PNGs
+# are throwaway debug artifacts that shouldn't be tracked.
+/*.png