Add yt-dlp "Download Video" Chromium extension

Download the current page's video with yt-dlp via Alt+Shift+D or a click
on the toolbar icon. A native-messaging host runs the download, shows live
progress on the Quickshell OSD, and posts a clickable "Download complete"
toast that opens the file in mpv.

- Extension: pinned key for a stable id, green download-video icon,
  keyboard command + toolbar action (reads the active tab URL).
- Native host (omarchy-chromium-ytdlp-host): verifies the URL with
  yt-dlp --simulate (else "No video found"), streams progress to the OSD
  (time-throttled to ~4/s), saves to ~/Videos, opens mpv on click.
- Installer (omarchy-install-chromium-ytdlp) writes the native-messaging
  manifest into installed Chromium/Chrome/Brave/Edge profiles; wired into
  browser install and chromium refresh, with a migration for existing users.
- omarchy-osd: add -d/--duration so the OSD can persist during a download.
- Add yt-dlp to base packages, load the extension via --load-extension,
  and document the Alt+Shift+D binding.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/shell.d/chromium-ytdlp-test.sh

@@ -0,0 +1,50 @@
+#!/bin/bash
+
+set -euo pipefail
+
+source "$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)/base-test.sh"
+
+TMPDIR=""
+
+export PATH="$ROOT/bin:$PATH"
+
+cleanup() {
+  [[ -n $TMPDIR && -d $TMPDIR ]] && rm -rf "$TMPDIR"
+}
+trap cleanup EXIT
+
+require_command jq
+
+TMPDIR=$(mktemp -d)
+test_home="$TMPDIR/home"
+manifest_path="$test_home/.config/chromium/NativeMessagingHosts/com.omarchy.ytdlp.json"
+
+HOME="$test_home" OMARCHY_PATH="$ROOT" omarchy-install-chromium-ytdlp
+
+[[ -f $manifest_path ]] || fail "yt-dlp native host installer creates fresh Chromium profile root"
+pass "yt-dlp native host installer creates fresh Chromium profile root"
+
+jq -e --arg path "$ROOT/bin/omarchy-chromium-ytdlp-host" '
+  .name == "com.omarchy.ytdlp" and
+  .path == $path and
+  (.allowed_origins | index("chrome-extension://dedjgknigfeelejglamclffonmophnfl/"))
+' "$manifest_path" >/dev/null
+pass "yt-dlp native host manifest uses Omarchy host path and extension id"
+
+parse_result=$(bash -c '
+  OMARCHY_PATH="$3"
+  source "$1"
+  parse_url "$2"
+' bash "$ROOT/bin/omarchy-chromium-ytdlp-host" '{"url":"https://example.test/watch?v=\"quoted\"&name=a\\b"}' "$ROOT")
+
+[[ $parse_result == "https://example.test/watch?v=\"quoted\"&name=a\\b" ]] ||
+  fail "yt-dlp native host parses escaped JSON URLs" "$parse_result"
+pass "yt-dlp native host parses escaped JSON URLs"
+
+bash -c '
+  OMARCHY_PATH="$3"
+  source "$1"
+  valid_url "$2"
+' bash "$ROOT/bin/omarchy-chromium-ytdlp-host" "javascript:alert(1)" "$ROOT" &&
+  fail "yt-dlp native host rejects non-web URLs"
+pass "yt-dlp native host rejects non-web URLs"