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/git-clean.fish

@@ -8,12 +8,13 @@
 #   git-clean [-h] [-f]
 #
 # DESCRIPTION
-#   Fetches and prunes the remote, updates the current branch, and deletes
-#   local branches whose tracking remote has been deleted. Automatically moves
-#   to main if currently on an orphaned branch.
+#   Fetches and prunes the remote, fast-forwards the current branch, and
+#   deletes local branches whose tracking remote has been deleted. Switches to
+#   main/master automatically if the current branch is orphaned.
 #
 # ARGUMENTS
-#   -h, --help   Show help message
+#   -h, --help    Show help message
+#   -f, --force   Force-delete unmerged branches too
 #   -f, --force  Force-delete unmerged orphaned branches (git branch -D)
 #
 # RETURNS