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/gi.fish

@@ -9,8 +9,9 @@
 #
 # DESCRIPTION
 #   Generates .gitignore content by querying the gitignore.io API. Appends
-#   results to the repository's .gitignore with MD5-based deduplication, or
-#   prints to stdout with -s. Supports boilerplate and interactive prompt modes.
+#   results to the repository's .gitignore with MD5-based deduplication —
+#   patterns already present are not re-appended — or prints to stdout with
+#   -s. Supports generic boilerplate and interactive prompt modes.
 #
 # ARGUMENTS
 #   -h, --help         Show help message
@@ -19,7 +20,7 @@
 #   -b, --boilerplate  Append boilerplate from $GITIGNORE_BOILERPLATE
 #   -p, --prompt       Prompt for patterns to append
 #   -s, --stdout       Print API output to stdout instead of .gitignore
-#   targets            Comma-separated list of language/tool names
+#   targets            Comma- or space-separated list of language/tool names
 #
 # RETURNS
 #   0  Patterns appended or printed