refactor: convert json-pretty format skill to a command

Move from skills/ to commands/ so it shows as /json-pretty:format
in the autocomplete menu with the plugin name prefix. Move the
script to scripts/ to match command-based plugin conventions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plugins/json-pretty/commands/format.md

@@ -1,6 +1,6 @@
 ---
-name: format
-description: Format, validate, or minify JSON without external online services
+description: "Format, validate, or minify JSON without external online services"
+allowed-tools: Bash
 ---
 
 ## When to Use
@@ -15,9 +15,9 @@ Use when the user asks to:
 
 ## Tool Location
 
-`~/.claude/skills/json-pretty/json-pretty.py`
+`${CLAUDE_PLUGIN_ROOT}/scripts/json-pretty.py`
 
-Symlinked to `~/.local/bin/json-pretty` for PATH access.
+Also symlinked to `~/.local/bin/json-pretty` for PATH access.
 
 ## Usage