gui: native-backend session work + fix shim crashes; add page smoke test

Bundles the pending native-UI session (dark shell, style overhaul, audio
page) with review fixes:
- native Row: set_subtitle_lines + set_activatable_widget (store and
  online-accounts pages crashed with AttributeError under TANINUX_UI=native)
- wine page routed through the ui seam (last direct Adw import removed)
- console: delete no-op log_expander/collapsible_log and .clear() call sites
- ui/__init__ docstring now states the actual default backend (native)
- tests/test_pages_native.py builds every registered page under the native
  backend (29 pass; skips headless)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

HANDOVER.md

@@ -177,3 +177,117 @@ Installed to `~/.local/share/icons/Tanin-*` (user dir, not pacman).
 - `camel.toml` `rebuilt_aur` list is stale (missing librewolf-bin, arch-update,
   timeshift-autosnap, xdg-terminal-exec).
 - Manual icon picker in `desktop.py` still lists all 5 `Tanin-*` themes (minor).
+
+---
+
+## SESSION 2026-06-27 — TANINUX Music scaffold (native TIDAL client, "Weg 3")
+
+New package `src/taninux/music/` — a native Apple-Music-style TIDAL client. Strategy:
+**reuse High Tide's UI-free backend, build our own native shell** (no libadwaita fork).
+High Tide's shell is built on heavy Adw layout widgets (NavigationView, OverlaySplitView,
+MultiLayoutView, Breakpoints, Carousel) that have no plain-GTK4 equivalent and that our
+`native.py` does NOT cover — so forking its UI was rejected. Its *backend* (~1650 LOC:
+GStreamer player, tidalapi session, token store) is cleanly decoupled and worth reusing.
+
+### Structure
+- `backend/player.py` — copied verbatim from High Tide's `lib/player_object.py` (GPL-3.0),
+  except ONE edit: `from . import discord_rpc, utils` → `from . import discord_rpc` +
+  `from . import state as utils`. Player's only coupling to the old god-`utils` was 4 names
+  (`CACHE_DIR`, `MUSIC_DIR`, `session`, `send_toast`) — all provided by `state.py`.
+- `backend/state.py` — slim shim providing those 4 names + `init()`/`set_session()`/`set_toast_sink()`.
+- `backend/secret_store.py` — copied from High Tide (LGPL-3.0), schema/key renamed to TANINUX.
+- `backend/auth.py` — extracted PKCE flow (was in an Adw.Dialog): `Auth.try_restore()` /
+  `pkce_login_url()` / `finish_pkce_login()` + `login_async()`.
+- `backend/discord_rpc.py` — no-op stub (player calls `set_activity`/`disconnect`).
+- `ui/transport.py` — bottom now-playing bar, binds to player GObject signals
+  (`song-changed`, `update-slider`, `notify::playing`, `can-go-*`). Async cover fetch.
+- `ui/library.py` — favorites-tracks list; row-activate → `player.play_this(tracks, i)`.
+- `ui/login_dialog.py` — native `ui.Dialog` PKCE login (tidalapi imported lazily inside).
+- `window.py` — shell: sidebar (nav) + `Gtk.Stack` content + transport bar. `tn-dark`.
+- `app.py` — entry `tmusic`. Lazy-imports player/auth (so app loads without tidalapi → shows
+  "backend missing" StatusPage). Flow: CSS → state.init → Auth → try_restore? → shell ±login.
+- CSS appended to `gui/ui/style_apple.css` (section "TANINUX Music"): `.tn-transport`,
+  `.tn-content`, `.tn-track-list`, `.tn-music-sidebar`. Reuses existing `.tn-sidebar`.
+- Entry point added to `pyproject.toml`: `tmusic = "taninux.music.app:main"`.
+
+### Verified
+- All new files `py_compile` clean. Backend `state`/`discord_rpc` import without tidalapi/Adw.
+- All UI+app modules import without tidalapi (lazy imports hold).
+
+### NOT verified (needs real env)
+- End-to-end playback: `tidalapi` is NOT installed here, and there's no TIDAL account/display
+  in the sandbox. **To run:** `pacman -S python-tidalapi` (or `pip install tidalapi`), then
+  `PYTHONPATH=src python -m taninux.music` (or `tmusic` after install). Expect: login dialog →
+  paste redirect URL → library loads → click track → GStreamer plays → transport updates.
+
+### Next building blocks (all go into the content `Gtk.Stack`)
+- Home page (mixes/recommendations carousels) and Search page (currently placeholders).
+- The "few missing native layout widgets" if richer nav is wanted: a NavigationStack
+  (push/pop with back button) and horizontal carousels. v1 deliberately uses a flat `Gtk.Stack`.
+- Toast sink: `state.set_toast_sink(...)` is wired but app currently leaves the default (logs).
+
+---
+
+## SESSION 2026-06-27 (cont.) — TANINUX Music FULL build + playback verified
+
+User gave full autonomy ("entwickle die app komplett aus"). The scaffold above is now a
+working app. **Playback verified end-to-end** via a headless test (logged-in PKCE session →
+favorite track → GStreamer pipeline reached PLAYING, position advanced to 8.2s).
+
+### Login: must be PKCE, not device-flow (IMPORTANT)
+- tidalapi has TWO clients. The OAuth **device-flow** (`session.login_oauth()`, the smooth
+  `link.tidal.com/XXXXX` flow) logs in and can BROWSE, but **cannot stream** — playback hits
+  `429 Too Many Requests` on `playbackinfopostpaywall`. tidalapi docstring: PKCE "is the only
+  way" to stream.
+- So login uses **PKCE** (`auth.pkce_login_url()` → browser → copy the redirect/"Oops" URL →
+  `finish_pkce_login`). `LoginDialog` auto-opens the browser, shows a clickable link, AND
+  watches the clipboard (`Gdk.Clipboard.read_text_async` poll) so pasting is automatic.
+- `auth.try_restore()` discards any stored NON-pkce token (`is-pkce` flag in keyring) to force
+  a PKCE re-login. Tokens persist in libsecret → normally no dialog on subsequent launches.
+
+### Runtime deps installed this session (pacman)
+- `python-tidalapi` (extra) — the API/player lib.
+- `gst-libav` + `gst-plugins-bad` + `gst-plugins-ugly` — **required for audio**. Without them
+  GStreamer can't decode TIDAL's AAC/DASH streams ("No suitable plugins found", no sound).
+  Key elements now present: `avdec_aac`, `avdec_flac`, `faad`, `dashdemux2`.
+- These are NOT expressible in pyproject; package them as distro deps for the [tanin] repo.
+
+### Architecture (all under src/taninux/music/)
+- `backend/api.py` — thin tidalapi data layer (UI-free): `home/explore/for_you_categories`,
+  `search`, favorites/playlists, `album_tracks`/`playlist_tracks`/`mix_items`/`artist_*`,
+  item classification (`item_kind/title/subtitle`), `IdCache`. NOTE: `session.home()` returns
+  400 sometimes → `home_categories()` falls back to legacy endpoint, and HomePage also pulls
+  `explore()` + `for_you()`.
+- `ui/images.py` — async cover loader, disk cache under `state.IMG_DIR`, sets `Gdk.Texture`
+  on `Gtk.Picture`.
+- `ui/nav.py` — `NavigationStack` (back button + title + content; set_root/push/pop). Replaces
+  Adw.NavigationView.
+- `ui/context.py` — `MusicContext(session, player, nav, toast)`; `open_item(item)` classifies +
+  pushes the right detail page; `play/shuffle`. Passed to all pages/widgets (no globals).
+- `ui/widgets.py` — `Card` (cover+title+sub, click→open_item), `Carousel` (titled h-scroll),
+  `TrackList` (row-activate → play).
+- `ui/pages_base.py` — `LoadablePage` (spinner → thread fetch() → main-thread build()).
+- `ui/pages_home.py`, `pages_search.py` (live clipboard-less SearchEntry → debounced search),
+  `pages_detail.py` (Album/Playlist/Mix share `_TrackDetailPage`; ArtistPage), `pages_collection.py`
+  (Bibliothek: playlists/albums/artists/tracks), `pages_queue.py`.
+- `window.py` — shell: sidebar (Home/Suchen/Bibliothek) → `nav.set_root`; Gtk.Overlay for
+  toasts; `TransportBar` at bottom. `reload_after_login()`.
+- `ui/transport.py` — now-playing bar: cover, prev/play/next, seek, shuffle/repeat/queue, volume.
+- `backend/mpris.py` — ported from High Tide, DECOUPLED: `MPRIS(player, app_id, raise_cb, quit_cb)`,
+  cover path via `state.IMG_DIR`. Verified on bus as `org.mpris.MediaPlayer2.ch.gabrielevarano.Taninux.Music`.
+- `app.py` — entry `tmusic`. CSS → state.init → Auth → try_restore? → shell ±PKCE login; wires
+  toast sink + starts MPRIS (both non-fatal).
+- CSS: "TANINUX Music" section in `gui/ui/style_apple.css` (cards/covers/carousel/transport/
+  toast/nav + title-1/title-3/dim-label/error fallbacks).
+
+### Known minor issues / TODO
+- Cosmetic GTK warning "GtkGizmo (slider) reported min width -4" from a `Gtk.Scale` — harmless.
+- Per-section nav stacks are not preserved: switching sidebar resets that section to its root
+  (Apple keeps a stack per tab). Acceptable for v1.
+- Queue page is read-only (no reorder/remove). No lyrics page. `discord_rpc` is a no-op stub.
+- DONE (2026-06-27 cont.): track→album/artist navigation — TrackRow has a "⋯" MenuButton +
+  right-click popover (Zum Album / Zum Interpreten / Als Nächstes / Zur Warteschlange); the
+  transport bar's title→album and artist→artist are clickable (`.tn-link`). Carousel cards
+  already opened detail pages. Sidebar switched to the Settings `.tn-nav` look (glassy accent
+  wash + a frost gradient on `window.tn-dark .tn-sidebar`).
+- Search is debounced via SearchEntry's `search-changed`; could add a small delay/throttle.