Use published site URL for Git Worktrees cross-link (#82)

## What

`Modules/Repository-Defaults.md`'s link to Git Worktrees was originally
dead (relative path removed when Ways-of-Working moved to MSXOrg/docs).
That was independently fixed on `main` in #79, but using a raw GitHub
blob URL (`github.com/MSXOrg/docs/blob/main/...`).

This PR updates it to the published site URL
(`msxorg.github.io/docs/Ways-of-Working/Git-Worktrees/`), matching the
pattern used by every other cross-org link in this repo (see
`src/docs/index.md`, `template-quickstart.md`,
`Process-PSModule/index.md`, etc.).

## Why

Consistency — readers get the rendered docs site instead of raw markdown
source, same as all other MSXOrg/docs references in this repo.

## Validation

Confirmed the site URL resolves (301 →
`msx.no/Ways-of-Working/Git-Worktrees/`, live content present). Branch
merged with latest `main` (#79), no other diffs remain.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: MariusStorhaug

src/docs/Modules/Repository-Defaults.md

@@ -54,7 +54,7 @@ Local work should use the organization worktree convention:
 - `main/` tracks the default branch.
 - Feature worktrees use `<type>-<slug>` directories and `<type>/<slug>` branches.
 
-For branch and worktree details, see [Git Worktrees](https://github.com/MSXOrg/docs/blob/main/src/docs/Ways-of-Working/Git-Worktrees.md).
+For branch and worktree details, see [Git Worktrees](https://msxorg.github.io/docs/Ways-of-Working/Git-Worktrees/).
 
 ## Default repository layout