Fix "in N minutes" parsing and VHS tape errors

- Strip "in " prefix before passing to date -d (was always broken)
- Fix quickstart tape: -B3 → -B4 for resume grep (Job: is 4 lines back)
- Fix notifications tape: -f ~/backup.sh → -c (file doesn't exist)

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

demo/editmode.tape

@@ -0,0 +1,78 @@
+# systab — Edit Mode with Notification Flags
+# Demonstrates the crontab-style editor with :flags syntax.
+
+Output demo/editmode.gif
+Set Shell bash
+Set Width 1200
+Set Height 600
+Set FontSize 16
+
+Set TypingSpeed 50ms
+
+Sleep 1s
+
+# First create some jobs to edit
+Type "# Create some jobs to work with"
+Enter
+Sleep 500ms
+Type "systab -t 'every 5 minutes' -c 'echo ping'"
+Enter
+Sleep 2s
+Type "systab -t daily -c '/home/user/backup.sh' -i"
+Enter
+Sleep 2s
+
+# Open edit mode with EDITOR=nano for visibility
+Type "# Open edit mode — add notifications, create and modify jobs"
+Enter
+Sleep 1s
+Type "EDITOR=nano systab -E"
+Sleep 500ms
+Enter
+Sleep 3s
+
+# In nano: navigate to the end of the file
+# Ctrl+V = page down in nano, then Down to reach last line
+Ctrl+V
+Sleep 500ms
+Down 5
+Sleep 500ms
+
+# Add a new job line with notification flags
+Type "new:i,e=admin@example.com | hourly | curl -s https://example.com/health"
+Sleep 1s
+Enter
+
+Sleep 1s
+
+# Save and exit nano
+Ctrl+O
+Sleep 500ms
+Enter
+Sleep 500ms
+Ctrl+X
+Sleep 3s
+
+# Show the result
+Type "# See the changes applied"
+Enter
+Sleep 500ms
+Type "systab -S"
+Sleep 500ms
+Enter
+Sleep 4s
+
+# Re-open edit mode to show flags are persisted
+Type "# Re-open edit mode — flags are persisted"
+Enter
+Sleep 1s
+Type "EDITOR=nano systab -E"
+Sleep 500ms
+Enter
+Sleep 3s
+
+# Just view and exit without changes
+Ctrl+X
+Sleep 2s
+
+Sleep 2s