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, 55 insertions, 0 deletions

diff --git a/docs/operation/boot-options.md b/docs/operation/boot-options.md
new file mode 100644
index 00000000..3c33ee3e
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+++ b/docs/operation/boot-options.md
@@ -0,0 +1,55 @@
+---
+lastproofread: '2025-11-14'
+---
+
+(boot-options)=
+
+# Boot Options
+
+:::{warning}
+This function can disrupt services.
+Run it only when necessary, and verify all input values before proceeding.
+:::
+
+VyOS provides several kernel command-line options to modify the normal boot
+process.
+To add an option, select the desired image in the GRUB menu at load time.
+Type **e** to edit the first line, then type **Ctrl+X** to boot.
+
+```{image} /_static/images/boot-options.webp
+:align: center
+:width: 80%
+```
+
+
+## Specify custom config file
+
+You can use a configuration file instead of the default `/config/config.boot`
+file. If the specified file doesn't exist or isn't readable, the system uses the
+default configuration file. No additional verification is performed, so specify
+a valid configuration file.
+
+```none
+vyos-config=/path/to/file
+```
+
+To load the *factory default* configuration, use:
+
+```none
+vyos-config=/opt/vyatta/etc/config.boot.default
+```
+
+
+## Disable specific boot process steps
+
+These options disable certain steps in the boot process. Understand the
+{ref}`boot process <boot-steps>` before using them.
+
+:::{glossary}
+no-vyos-migrate
+   Do not perform config migration.
+
+no-vyos-firewall
+   Do not initialize default firewall chains, renders any firewall
+   configuration unusable.
+:::