feat: flip swap mechanism — MD as primary, RST as override (Phase 1)

This is the first of three phases inverting the per-page swap mechanism
so MD becomes the canonical primary and RST becomes the rare override.

Phase 1 — file renames + conf.py exclude_patterns flip only:
- Rename docs/**/md-<stem>.md to docs/**/<stem>.md (drop md- prefix)
  for all 254 stems previously listed in docs/_swap.txt
- Rename docs/**/<stem>.rst to docs/**/rst-<stem>.rst (add rst- prefix)
  for the same 254 stems
- Repurpose docs/_swap.txt as docs/_rst_overrides.txt; initially empty
  comment-only since no pages need the RST fallback right now
- conf.py exclude_patterns flipped: rst-*.rst is now excluded by default
  instead of md-*.md
- conf.py runtime-artifact references updated to _rst_override_state.json
  and _md_exclude.txt (Phase 2 will rewrite swap_sources.py to produce
  these names; for now no swap script runs because overrides list is empty)

Phase 2 (next commit on this branch) will rewrite scripts/swap_sources.py
with inverted rename direction, delete scripts/import_myst.py + tests, and
update tests/test_swap_sources.py for the new semantics.

Phase 3 will be the cleanup pass and ready-for-review flip.

Generated by robots https://vyos.io

1 files changed, 45 insertions, 0 deletions

diff --git a/docs/contributing/cla.md b/docs/contributing/cla.md
new file mode 100644
index 00000000..01323111
--- /dev/null
+++ b/docs/contributing/cla.md
@@ -0,0 +1,45 @@
+---
+lastproofread: '2025-12-05'
+---
+
+(cla)=
+
+# Contributor License Agreement
+
+Before we can accept your contributions to VyOS, you must sign a **Contributor
+License Agreement (CLA)**.
+
+This is a standard open-source practice that protects both you and the project.
+
+The process is straightforward and fully automated:
+
+1. **Review the CLA document**
+
+   Find the CLA text in our
+   [GitHub repository](https://github.com/vyos/vyos-cla-signatures/).
+
+2. **Submit a pull request**
+
+   When you open a pull request, a CLA bot automatically checks whether all
+   commit authors have signed the CLA.
+
+3. **Follow the bot's instructions**
+
+   If the CLA has not been signed, the bot leaves a comment with instructions.
+   Reply to that comment with the suggested text to sign the CLA.
+
+4. **Wait for confirmation**
+
+   The CLA bot verifies your response and updates the pull request status.
+   Once all commit authors have signed, the bot confirms that the CLA
+   requirement is met and unlocks the pull request for merging.
+
+:::{note}
+Each commit author must sign the CLA.
+
+If your pull request includes commits from multiple contributors, each one
+must sign the CLA before the pull request can be accepted.
+:::
+
+Once you sign the CLA, it remains valid for all your past and future
+contributions to VyOS under the same GitHub identity.