Remove the deprecated legacy slash commands

adjust worktree handling and defer to harness tools when avail (PRI-974)

commands/brainstorm.md

@@ -1,5 +0,0 @@
----
-description: "Deprecated - use the superpowers:brainstorming skill instead"
----
-
-Tell your human partner that this command is deprecated and will be removed in the next major release. They should ask you to use the "superpowers brainstorming" skill instead.

commands/execute-plan.md

@@ -1,5 +0,0 @@
----
-description: "Deprecated - use the superpowers:executing-plans skill instead"
----
-
-Tell your human partner that this command is deprecated and will be removed in the next major release. They should ask you to use the "superpowers executing-plans" skill instead.

commands/write-plan.md

@@ -1,5 +0,0 @@
----
-description: "Deprecated - use the superpowers:writing-plans skill instead"
----
-
-Tell your human partner that this command is deprecated and will be removed in the next major release. They should ask you to use the "superpowers writing-plans" skill instead.

skills/using-git-worktrees/SKILL.md

@@ -168,7 +168,6 @@ Ready to implement <feature-name>
 | Permission error on create | Sandbox fallback, work in place |
 | Tests fail during baseline | Report failures + ask |
 | No package.json/Cargo.toml | Skip dependency install |
-| Plan touches multiple repos | Create a matching worktree in each repo, same branch name |
 
 ## Common Mistakes