fix(modules-2,6,7,8,9,10,14): deterministic main branch + correct two claims

- M2 lab now `git init -b main` (with older-git fallback note) so every later
  `main` reference resolves; reconciled M3/M6/M7/M8 wording and M10's standalone
  review-lab repo (`git init -qb main`).
- M9: replace "issues are on by default on every forge" with a provider-neutral
  version naming the exceptions (Bitbucket/Azure DevOps/SourceHut).
- M14: qualify "hosted runners need zero setup" — true for SaaS forges; the
  self-hosted track needs a runner attached (Module 19). Both paths stay valid.

Closes #5
Closes #13
Closes #16

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TfzV5QvtPDz8LJS3Pu5VLT

modules/08-remotes-and-hosting/README.md

@@ -119,8 +119,9 @@ the "someone else" was the host's auto-generated README.)
 **3. Branch-name mismatch.** Your local default branch is `master` but the host expects `main` (or
 vice versa). `git push -u origin main` then errors with `src refspec main does not match any`. Fix:
 check what you actually have with `git branch`, and either push the branch you have
-(`git push -u origin master`) or rename it first (`git branch -m main`). Worth settling early so it
-doesn't confuse you for the rest of the course.
+(`git push -u origin master`) or rename it first (`git branch -m main`). If you initialized with
+`git init -b main` back in Module 2, you're already on `main` and this one won't bite you here — but
+it's the classic wall for any repo that started life on `master`, so it's worth recognizing.
 
 ### Pull, fetch, and the everyday loop