fix(cron): add one-time reminders and fix data paths to workspace

- Add at_seconds parameter for one-time reminders (e.g., "remind me in 10 minutes")
- Update every_seconds description to emphasize recurring-only usage
- Route cron delivery: deliver=true sends directly, deliver=false uses agent
- Fix cron data path from ~/.picoclaw/cron to workspace/cron
- Fix sessions path from workspace/../sessions to workspace/sessions

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

.gitignore

@@ -1,3 +1,4 @@
+# Binaries
 bin/
 *.exe
 *.dll
@@ -5,12 +6,21 @@ bin/
 *.dylib
 *.test
 *.out
+/picoclaw
+/picoclaw-test
+
+# Picoclaw specific
 .picoclaw/
 config.json
 sessions/
+build/
+
+# Coverage
 coverage.txt
 coverage.html
-.DS_Store
-build
 
-picoclaw
+# OS
+.DS_Store
+
+# Ralph workspace
+ralph/