docs(functions): merge remaining manual-only facts into headers

Word-level diff of every manual entry against its generated counterpart
surfaced 546 tokens present in the manual and absent from the header —
losses reconcile.py missed, because it compared description length and
these headers are longer overall thanks to ARGUMENTS/RETURNS.

Merged the substantive ones (546 -> 202 residual tokens, the remainder
being synonym drift). Notable real fixes:

- git-clean: -f/--force was missing from ARGUMENTS entirely
- pkg: per-package-manager query table
- qc: cli-role rationale, role paths, --role passthrough
- config-help: site URL, xdg-open, man page path, case-insensitivity
- agents-init: idempotency, .gitignore paths, upstream pull, wrapper callers
- smart_exit: exit-builtin wiring note, $SCROLLBACK_HISTORY_DIR

The manual's claim that claude/agy pass `agents-init --agents` is stale;
both pass `--quiet` (full setup). Header wins, manual dropped.

functions/config-help.fish

@@ -17,11 +17,14 @@
 #   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. Pass --html / -w to open the published documentation website in
-#   the default browser (deep links to a section aren't supported there —
-#   use the site's search box). Pass --man / -m to open the compiled man
-#   page; if a section keyword is given, the pager opens at the nearest
-#   match. Pass --help or -h for usage.
+#   screen. Section matching is case-insensitive. Pass --html / -w to open
+#   the published documentation website (https://fish-config-docs.pages.dev/)
+#   in the default browser via xdg-open — deep links to a section aren't
+#   supported there, so if a keyword is given a note points you to the site's
+#   search box instead. Pass --man / -m to open the compiled man page
+#   (docs/fish-config.1) via `man -l`; if a section keyword is given, the
+#   pager opens at the nearest match. Pass --help or -h for usage and the
+#   navigation key reference.
 #
 # ARGUMENTS
 #   section     Optional keyword to jump to a matching section heading