Description

Release 1. With a selection, a shortcut wraps it: bold (**), italic (_), inline code (backtick), and link (sel). Toggle off if already wrapped. With no selection, insert the empty pair with the cursor between. Needs free keys (Ctrl+B is new-inbox; pick non-conflicting bindings, document them). Keep the markup-visible invariant (the markers are inserted into the buffer).

Acceptance Criteria

• #1 Selection wraps in **/_/code/link via shortcuts; toggles off when already wrapped
• #2 No selection inserts the pair with the cursor inside
• #3 Bindings chosen to not clash with existing keys; documented