docs(functions): drop backticks from doc-headers

CONTRIBUTING states doc-headers are written as plain text -- the header
is read as-is by config-help, by funcsave, and by anyone opening the
file, and docs/codespans.py adds the site's inline code spans at render
time. 22 files had drifted from that, carrying 41 hand-written spans
that reached config-help and the man page as literal backtick
characters inside an otherwise verbatim block.

The one span whose content ended in a space is requoted rather than
dropped, so "read> " keeps reading as a prompt string.

functions/_agents_init_ensure_gitignore.fish

@@ -6,9 +6,9 @@
 #
 # DESCRIPTION
 #   Appends any patterns not already covered by the project's .gitignore.
-#   Uses `git check-ignore` for accurate rule matching (catches wildcards
+#   Uses git check-ignore for accurate rule matching (catches wildcards
 #   and parent-dir globs). Falls back to a plain string search when the
-#   root is not a git repository. Leading `/` is stripped from each pattern
+#   root is not a git repository. Leading / is stripped from each pattern
 #   before the path-based check so root-anchored patterns (e.g. /AGENTS.md)
 #   are matched correctly.
 #