Teach the launcher what an operating system knows

The OS-parity batch from the vicinae plan, tasks 1 through 7. The audit
came back better than the plan guessed: the calculator already links
libqalculate, the built-in file index answers in under 100ms across all
of home, quicklinks and snippets ship as built-in stores -- so zero new
packages, and `vicinae dmenu` replaces the planned compiled extension
outright. What was missing gets built: a power menu (lock, suspend, log
out through uwsm, restart, power off), reminders as transient systemd
timers with a pick-to-cancel list, a color picker over hyprpicker, and
dmenu pick-lists for window switching, force quit, kill process, SSH
hosts, and recent files -- all through one panama-pick helper. The
launcher commands contract exercises the reminder parsing and every
pick-list against stubs, including killing its own sacrificial sleep.

config/local/share/vicinae/scripts/lock-screen

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+# @vicinae.schemaVersion 1
+# @vicinae.title Lock Screen
+# @vicinae.mode silent
+# @vicinae.icon ../../icons/hicolor/scalable/apps/panama-settings.svg
+# @vicinae.description Lock the session now.
+# @vicinae.keywords ["lock", "screen", "away", "secure"]
+
+# The logind signal, same as the CTRL+ALT+L bind: hypridle is the one listener
+# and owns actually running hyprlock.
+exec loginctl lock-session