docs: publish docs/ to the GitHub wiki and reorganise the user guide

- scripts/publish-wiki.sh publishes every page listed in SECTIONS, copies
  images, writes a sectioned sidebar and footer, and removes stale pages.
  --check fails on links to missing files or headings and on docs pages
  that are neither published nor excluded.
- New wiki.yml runs the check on pull requests and pushes to main, and
  publishes when release.yml calls it or when started by hand.
- Split USER_GUIDE.md into topic pages (files, synced folders, photos,
  sharing, computers, launcher and tray); add Getting started and FAQ.
- Make the COPR repository the main Fedora path, with update and
  uninstall steps for every package type.
- Fix the stale CAPTCHA note in CLI.md, document pdfs unlock and lock,
  and drop the broken AGENTS.md link from CONTRIBUTING.md.

docs/DEVELOPMENT.md

@@ -141,10 +141,25 @@ file to `po/POTFILES.in`, run `po/update.sh`, and translate the new entries in e
 unit test, a simulation scenario or a `regression B<n>` acceptance case, and cite the entry in the
 code as `docs/BUGS.md B<n>`. Do not cite planning notes that are not in the repository.
 
-**A user-visible change.** Update the matching page (user guide, CLI reference, configuration)
-and the `[Unreleased]` section of [CHANGELOG.md](CHANGELOG.md). `scripts/publish-wiki.sh` copies
-the six user pages (`INSTALL`, `USER_GUIDE`, `CLI`, `CONFIGURATION`, `TROUBLESHOOTING`, `RECOVERY`)
-to the GitHub wiki, so keep their file names.
+**A user-visible change.** Update the matching page (a user guide topic, the CLI reference,
+configuration) and the `[Unreleased]` section of [CHANGELOG.md](CHANGELOG.md). Link between pages
+with relative links such as `[Conflicts](SYNCED_FOLDERS.md#conflicts)`, and show screenshots from
+`images/` with `../images/<name>.png`.
+
+**The wiki.** `docs/` is the source of the [GitHub wiki](https://github.com/narrrl/proton-drive-linux/wiki).
+`scripts/publish-wiki.sh` turns each page listed in its `SECTIONS` into a wiki page, rewrites the
+links, copies the images and writes the sidebar. `docs/README.md` becomes the wiki's Home.
+`BUGS.md` and `CHANGELOG.md` stay out of it; the wiki links to them on GitHub.
+
+- `scripts/publish-wiki.sh --check` checks every link and heading anchor in `docs/`, `README.md`,
+  `CONTRIBUTING.md` and `SECURITY.md`. It fails on a page in `docs/` that is not in `SECTIONS`
+  or `EXCLUDED`. `.github/workflows/wiki.yml` runs it for every change to the documentation.
+- Each release publishes the wiki from the tag. Run the **Wiki** workflow from the Actions tab to
+  publish `main` in between, for example after fixing a mistake.
+- `scripts/publish-wiki.sh [WORKDIR]` builds and commits the wiki in a local clone without
+  pushing, so you can look at the result first. `--push` pushes it.
+
+Never edit the wiki in the browser: the next publish replaces every page.
 
 ## Releasing
 
@@ -162,7 +177,8 @@ Releases are cut from `main` by pushing a `v*` tag. `.github/workflows/release.y
 5. calls `.github/workflows/aur.yml`, which updates and pushes the AUR recipes and commits them
    back to `main`;
 6. calls `.github/workflows/copr.yml`, which builds the release in the
-   [COPR repository](../packaging/copr/README.md) (secret `COPR_CONFIG`).
+   [COPR repository](../packaging/copr/README.md) (secret `COPR_CONFIG`);
+7. calls `.github/workflows/wiki.yml`, which publishes `docs/` at the tag to the wiki.
 
 To prepare a release: