android: a folder of audio files, and a paste of track links

The paste door now reads itself the way the desktop's does: one track link
in the paste and every line is looked up on its own public page
(playlist_import_track_links), which is the way past Spotify's 100-track
public ceiling — the wait screen counts them as they arrive. A fourth door
imports a folder of audio files off this phone, picked with the storage
plugin's own document-tree picker; playlist_import_folder grew a path
argument for it, because on Android it had no dialog to open and always
answered nothing. A YouTube playlist link needed no door at all — the link
one already dispatches it.

ANDROID.md

@@ -349,14 +349,23 @@ describe / pin / duplicate / delete, `playlist_add_items`,
   desktop's commands already emit; the page re-reads its rows when the
   playlist's revision moves.
 - **Importing** (`importer.svelte.js`, `screens/Import.svelte`): the
-  shelf's Import opens the doors that need no file — a link (YouTube ·
-  Spotify · Apple Music · TIDAL · Deezer), a pasted tracklist (plain lines,
-  a timestamped setlist, or track links), a YouTube DJ set's posted
-  tracklist. The backend stages the draft over plain HTTP (the same
-  commands as the desktop, no yt-dlp involved), the review screen shows
-  every row's verdict, the stream rows are verified against the catalog
-  while it is up (the desktop's pass, verbatim), and Create swaps the
-  review for the playlist it made (`nav.replace`).
+  shelf's Import opens four doors — a link (YouTube · Spotify · Apple
+  Music · TIDAL · Deezer; a YouTube playlist link rides this one too, the
+  backend dispatches it by host), a pasted tracklist (plain lines, a
+  timestamped setlist, or track links), a YouTube DJ set's posted
+  tracklist, and a folder of audio files on this phone. A paste holding
+  even one track link takes the link path (`playlist_import_track_links`,
+  the desktop's own detector verbatim): each line is read off its own
+  public page — the way past Spotify's 100-track public ceiling — and the
+  wait screen counts them as they come. The folder door picks with the
+  storage plugin's document-tree picker and hands the resolved path to
+  `playlist_import_folder`, which grew a `path` argument for it: on the
+  phone that command had no dialog to open and always answered nothing.
+  The backend stages the draft over plain HTTP (the same commands as the
+  desktop, no yt-dlp involved), the review screen shows every row's
+  verdict, the stream rows are verified against the catalog while it is up
+  (the desktop's pass, verbatim), and Create swaps the review for the
+  playlist it made (`nav.replace`).
 - **The share sheet** (`crates/tauri-plugin-share`, `share.svelte.js`):
   Share → SoulStream from any app. The plugin's `ShareActivity` (an
   ACTION_SEND text/plain target, merged into the app's manifest from the
@@ -367,9 +376,9 @@ describe / pin / duplicate / delete, `playlist_add_items`,
   anything else the pasted-tracklist door. The phone walk sends the intent
   itself (`adb shell am start -a android.intent.action.SEND …`).
 
-Not on the phone yet: the file and folder import doors (the files are on
-the desktop), the listener door, drag reorder, the cover picker, export,
-Share on SoulStream.
+Not on the phone yet: the playlist-file door and export — both want a file
+picker the storage plugin has still to grow — the listener door (it needs
+yt-dlp, a desktop tool), drag reorder, and Share on SoulStream.
 
 ## Settings that reach the config
 
@@ -569,8 +578,9 @@ a catalog record, its Save and the Transfers burst → Gaps → the playlist
 shelf and a page with every row kind (a local row, the stream row through
 the resolver, the filter, a removal and its undo, unpin, rename, a new
 playlist, Add to playlist from a record's sheet, delete) → the import doors
-(a pasted tracklist, a link with its catalog verification, a share from
-another app) → the playlist repair (an unknown row relinked from the
+(a pasted tracklist, a link with its catalog verification, pasted track
+links read a page each, a folder of audio files off the phone, a share
+from another app) → the playlist repair (an unknown row relinked from the
 library) → the artwork viewer → a queue row's sheet → a catalog song's,
 a catalog card's and the record page's sheets → the now-playing Save →
 a peer's sheet, a raw file's sheet, a user's shares browsed and a folder
@@ -616,11 +626,12 @@ paused) without the walk.
   key, Who has it) — Freenet on the phone is a later experiment; the
   network side is in. Rooms and chat are built and mock-walked; a live room
   is Kyle's to join.
-- The desktop-only doors and tools: the file and folder playlist imports,
-  the listener door and the lyric alignment models (a desktop runtime),
-  playlist export, drag reorder (Move up / down / to the top stand in), catalog track
-  previews, the full discography page, the artist-artwork upscaler,
-  updates and the account section (sign-in lives on Community).
+- The desktop-only doors and tools: the playlist-file import and export (a
+  file picker the phone's storage plugin has still to grow), the listener
+  door and the lyric alignment models (a desktop runtime), drag reorder
+  (Move up / down / to the top stand in), catalog track previews, the full
+  discography page, the artist-artwork upscaler, updates and the account
+  section (sign-in lives on Community).
 - Follows and the play history are per library folder, so the phone's own
   folder starts empty of both; they arrive with a shared library.
 - The artwork viewer: the cover at full size, pinch to zoom, one finger