New captures go to the inbox bucket

New captures always go into doc/agile/product_backlog/inbox/, not near/ or far/.

Why: The inbox is the triage entry point; near and far are for captures that have already been reviewed and placed. Filing directly to near/far skips the triage step.

How to apply: When using compass add capture, always pass --parent-dir doc/agile/product_backlog/inbox. Move to near or far only after explicit triage with the user.