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/yt-dlp.fish

@@ -12,7 +12,8 @@
 #   (--sponsorblock-remove all, --embed-subs, --embed-metadata,
 #   --embed-thumbnail). Each default is suppressed if the user already
 #   passes that flag, its alias, or its negation (e.g. --no-embed-thumbnail
-#   drops our --embed-thumbnail). All other arguments pass through
+#   drops our --embed-thumbnail; --no-sponsorblock or your own
+#   --sponsorblock-remove drops ours). All other arguments pass through
 #   untouched. --help and friends fall through to real yt-dlp.
 #
 #   Opinionated component (C1): when disabled via __fish_config_op_aliases