docs(site): title Examples fences and auto-title file-scoped snippets

Function EXAMPLE blocks now render as their own fish fence titled
"Examples" (matching the existing "Usage" title on the Synopsis fence),
triggered by a flat Example: label line mirroring the Synopsis: prefix.

Prose pages get two new generic titling signals in _render_para: a bare
indented path ending in a known extension is titled by its basename, and
a leading "# in <file>" / "# <file>" comment on a shell paragraph is
promoted to the fence title and stripped from the body. This picks up
local.fish/secrets.fish path displays and override examples in
07-customization.md for free, plus a bonus .logging_disabled hit.

10-personalization.md's secrets.fish block gets an explicit "# secrets.fish"
comment to title it the same way. The four local.fish examples keep their
existing descriptive comments rather than a redundant local.fish title.

docs/manual/10-personalization.md

@@ -33,6 +33,7 @@ fish_variables (auto-managed by fish) is excluded from this repo via
 Store anything you would not commit to a public repo: API keys, auth tokens,
 passwords, and personal identifiers.
 
+    # secrets.fish
     set -gx MY_NAME "Your Name"
     set -gx MY_EMAIL "you@example.com"
     set -gx GPG_RECIPIENT "you@example.com"