docs: update site title and canonical URL

Rename the Starlight site to "Rootiest Fish Config" and switch its
canonical URL from the Cloudflare Pages subdomain to
fish-config.rootiest.fyi (now aliased in Cloudflare). Updates all
references in README, config-help, open-url, and the manual, and
regenerates the concat/man-page artifacts to match.

docs/fish-config.1

@@ -2421,7 +2421,7 @@ that matches the keyword. Lookup order: docs/fish-config.index (exact
 keyword aliases), then a normalized heading scan as fallback.
 When opened with ov a sticky navigation hint is shown at the top of the
 screen. Section matching is case-insensitive. Pass --html / -w to open
-the published documentation website (https://fish-config-docs.pages.dev/)
+the published documentation website (https://fish-config.rootiest.fyi/)
 in the default browser via xdg-open \[em] deep links to a section aren\[aq]t
 supported there, so if a keyword is given a note points you to the site\[aq]s
 search box instead. Pass --man / -m to open the compiled man page
@@ -2708,7 +2708,7 @@ Notes:
 
 Example:
 open-url https://git.rootiest.dev/rootiest/fish-config
-open-url -v https://fish-config-docs.pages.dev/
+open-url -v https://fish-config.rootiest.fyi/
 \f[R]
 .fi
 .PP
@@ -3695,7 +3695,7 @@ help config --html
 \f[R]
 .fi
 .PP
-Opens https://fish-config-docs.pages.dev/ in the default browser \[em]
+Opens https://fish-config.rootiest.fyi/ in the default browser \[em]
 the Starlight-powered site built from \f[V]docs/manual/**\f[R] on every
 push to \f[V]main\f[R].
 It has a section sidebar and full-text search.