docs(tools/prompts): remove redundant per-prompt headings

The fastmcp-prompt directive now creates its own section with a hidden
title (for TOC / {ref} resolution) and a visible card header. The outer
## `run_and_wait` / ## `diagnose_failing_pane` etc. headings caused the
prompt name to appear twice — once as the section heading immediately
above the card, and once in the card's own signature line.

With the headings removed, each prompt name appears exactly once: in the
card header, with the new ¶ permalink from the directive-created section.
The intro bullet {ref} cross-refs continue to resolve correctly.

Author: tony

docs/tools/prompts.md

@@ -29,8 +29,6 @@ tools instead.
 
 ---
 
-## `run_and_wait`
-
 ```{fastmcp-prompt} run_and_wait
 ```
 
@@ -74,8 +72,6 @@ success or failure.
 
 ---
 
-## `diagnose_failing_pane`
-
 ```{fastmcp-prompt} diagnose_failing_pane
 ```
 
@@ -109,8 +105,6 @@ Something went wrong in tmux pane %1. Diagnose it:
 
 ---
 
-## `build_dev_workspace`
-
 ```{fastmcp-prompt} build_dev_workspace
 ```
 
@@ -171,8 +165,6 @@ across layout changes; window renames are not.
 
 ---
 
-## `interrupt_gracefully`
-
 ```{fastmcp-prompt} interrupt_gracefully
 ```