feat: Clear next steps after worktree creation

When user chooses to create a worktree, build.md now displays a clear
"ACTION REQUIRED" message explaining:
- What was created (worktree path, branch, plan)
- Exact command to open new VSCode window in worktree
- How to continue the build in the new window
- Why switching is necessary (Claude Code is directory-bound)

Bumps version to 1.0.4.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 All notable changes to Auto-Build plugin.
 
+## [1.0.4] - 2024-12-22
+
+### Improved
+- Clear "ACTION REQUIRED" message after worktree creation
+- Explicit next steps showing user must open new VSCode window in worktree
+- Explains why switching is necessary (Claude Code sessions are directory-bound)
+
 ## [1.0.3] - 2024-12-22
 
 ### Fixed