docs: graduate install instructions for the 3.0.0 release

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: johnlindquist

README.md

@@ -10,7 +10,7 @@ git diff | explain.md            # Pipe through any command
 
 ---
 
-## New in v3 (prerelease on the `next` tag)
+## New in v3
 
 **Markdown agents that evolve.** One file per agent. Any engine. Evals that
 prove behavior. Every run makes them better.

skills/mdflow/SKILL.md

@@ -29,7 +29,7 @@ the user. Dry runs are free.
 ## Step 0: is mdflow installed? (free)
 
 ```bash
-command -v md || npm i -g mdflow@next   # v3 prerelease; drop @next once 3.0 ships
+command -v md || npm i -g mdflow
 ```
 
 ## The roster convention