docs(functions): add missing EXIT STATUS header docs

Fills the gaps recorded in JOB-BRIEF-FINDINGS.md for the functions
converted to header-driven --help: 16 argument-less functions gain an
EXIT STATUS section (check_fish_deps, claude-docs, claude-pr, cleanup,
fast, fzf-update, gip, gip4, hist, limine-edit, lock, ports,
screensleep, steam-dl, swapstat, tmux-clean), and 8 functions that
already document ARGUMENTS gain EXIT STATUS too (lD, lsr, lss, lstree,
lt, ltr, lx, qr).

Not touched: gip6, ld, parur, sudo-toggle, upgrade, the JOB-BRIEF's
'missing ARGUMENTS' group. Re-checked their bodies against that claim
-- none of the five take a positional argument ($argv only appears
forwarded to the --help check), so an ARGUMENTS section would document
something that doesn't exist. All five already have EXIT STATUS.

functions/limine-edit.fish

@@ -13,6 +13,9 @@
 #   files tracked by sbctl. Combines the edit and sign steps into a single
 #   command.
 #
+# EXIT STATUS
+#   0  Always (individual step failures are not propagated)
+#
 # EXAMPLE
 #   limine-edit
 function limine-edit --description 'Safely edit and re-verify Limine configuration'