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/02-version-control-as-a-safety-net/README.md

@@ -61,7 +61,7 @@ minutes of work."
 The core commands:
 
 ```bash
-git init                 # turn the current folder into a repository (once per project)
+git init -b main         # turn the current folder into a repository, first branch named "main" (once per project)
 git status               # what's changed since the last commit?
 git add .                # stage the changes you want in the next commit
 git commit -m "message"  # save a checkpoint with a note
@@ -154,10 +154,17 @@ and your AI assistant.
 
    ```bash
    cd ~/workflow-course/tasks-app
-   git init
+   git init -b main           # start the repo with its first branch named "main" (Git 2.28+)
    git status                 # everything shows as "untracked" — Git sees the files but isn't saving them yet
    ```
 
+   > **Why `-b main`, and what if your Git is older.** Stock Git still names the first branch
+   > `master`, but every later module in this course says `main` (you'll `git switch main`, compare
+   > `git log main..HEAD`, merge into `main`). `git init -b main` settles that name once so those
+   > commands resolve. The `-b` flag needs Git 2.28+ (`git --version` to check); on an older Git, run
+   > plain `git init`, finish the first commit in step 2, then rename the branch once with
+   > `git branch -m master main`. Either route leaves you on `main`.
+
 2. Add a `.gitignore` so you don't version generated junk. Copy this module's
    `lab/gitignore-starter` to a file named exactly `.gitignore` in the project root, then: