chore(docs): retire wiki, chunked HTML, and split-manual pipeline

docs/manual/** plus the Astro Starlight site (https://fish-config-docs.pages.dev/)
replace the Gitea wiki (docs/wiki/) and chunked offline HTML (docs/html/,
docs/html-style.html) as the published documentation surface. Retires the
now-unused docs/split-wiki.py and docs/split-manual.py generators alongside them.

- config-help --html now opens the published site root instead of resolving
  a local sitemap anchor; when a keyword was given it prints a note that deep
  links aren't available yet and to use the site's search box.
- open-url and docs/manual/05-functions/14-miscellaneous.md examples
  repointed from docs/html/index.html to the site URL.
- docs/manual/11-viewing-this-manual.md rewritten to document the four
  access paths: the website, the man page, in-terminal pager, and reading
  docs/manual/** directly. fish-config.index updated to match the new
  headings.
- README.md documentation section and Zoxide attribution link repointed at
  the site; corrected the stale "single source file" claim about
  fish-config.md.
- Regenerated docs/fish-config.md via build-manual.py --concat.

docs/wiki/11-viewing-this-manual.md

@@ -1,74 +0,0 @@
-# 11. VIEWING THIS MANUAL
-
-**Sections:** [Index](index.md) | [1. Configuration Variables](1-configuration-variables.md) | [2. Path Setup](2-path-setup.md) | [3. Key Bindings](3-key-bindings.md) | [4. Abbreviations](4-abbreviations.md) | [5. Functions Reference](5-functions-reference.md) | [6. Dependency Catalog](6-dependency-catalog.md) | [7. Customization](7-customization.md) | [8. Fisher Plugins](8-fisher-plugins.md) | [9. Installation](9-installation.md) | [10. Personalization](10-personalization.md) | **11. Viewing This Manual**
-
----
-
-## With ov (recommended)
-
-    help config
-
-ov renders the Markdown with syntax highlighting and section-based
-navigation.
-
-    Space       next section
-    ^           previous section
-    Alt+u       toggle section list sidebar
-    /           search forward
-    n / N       next / previous search match
-    g           go to line number
-    j           interactive jump target (line, %, or 'section')
-    q           quit
-
-## With bat
-
-    bat --language=markdown --paging=always ~/.config/fish/docs/fish-config.md
-
-## As a man page
-
-    help config --man
-    help config pkg --man
-
-Opens the compiled docs/fish-config.1 directly via man -l, bypassing
-the pager fallback chain. If a section keyword is given, the pager opens
-at the nearest matching heading. The symlink is created once on first
-run (like an install step) and MANPATH is set each session, enabling
-the standard invocation:
-
-    man fish-config
-
-NOTE: fish-config (hyphen) is this config's man page. fish_config
-(underscore) is fish's built-in browser-based configuration tool —
-a completely separate command. Do not mix them up.
-
-## In the browser (HTML)
-
-    help config --html
-    help config pkg --html
-
-Opens docs/html/index.html in the default web browser. If a section
-keyword is given, the browser opens directly at the matching anchor
-(resolved via docs/html/sitemap.json). Browser detection queries the
-system's x-scheme-handler/https MIME entry (via xdg-mime) to find the
-real browser binary, then falls back through known browser binaries
-(firefox, chromium, vivaldi, etc.), and finally xdg-open as a last
-resort. Set $fish_help_browser or $BROWSER to override.
-
-## As a wiki
-
-The generated Markdown wiki lives in docs/wiki/. index.md provides the
-project overview and a full table of contents. Each section page has a
-navigation bar at the top linking to every other section.
-
-The wiki is auto-generated from this file by the CI pipeline on every
-push to main that changes docs/fish-config.md.
-
-## Jumping to a section
-
-    help config keybindings
-    help config abbreviations
-    help config pkg
-    help config logs
-    help config fish-deps
-
-The keyword is matched case-insensitively against section headings.