spec new — create a single task or req from template

CLI at scripts/specctl. Input: <type> <name> where <type> is task or req. If <name> contains /, the leading part is a topic folder.

Failure handling

Validate before doing any work:

• Missing or empty <name>: ask for the name; do not invent a placeholder.
• <type> not task or req: state the allowed values and stop; do not guess.
• Target file already exists: do not overwrite. Report the existing path and ask whether to open it, pick a new name, or confirm overwrite.

Step 1: Ensure .spec/ exists

ls .spec/ 2>/dev/null || mkdir -p .spec/tasks .spec/reqs

Step 2: Determine path