android: the long session — what the app is still holding after an hour

Every walk this project has ever run is minutes long, and nothing in the port
had been looked at for a leak. Driving the real bundle lap after lap says two
useful things. The first is that the obvious answer is wrong: the naive
add-minus-remove listener counter climbs about twelve a lap, and every one of
those is a `.screen` element that `{#key nav.seq}` threw away — count only
what is still attached to window, document or a connected element and it is
flat, lap for lap, and so are the intervals. The second is that exactly two
things grow without a limit. `art.svelte.js` kept every cover it had ever
fetched for the WebView's lifetime — one browse of a 114-cover library takes
it from 5 keys to 114 and gives nothing back, at roughly 63 KB of base64
each — and `pls.covers` is keyed `id:revision`, so every playlist edit
stranded a 360 px data URL under a key nothing could ever read again.

Both are bounded at the desktop's own numbers rather than at invented ones:
`ART_THUMB_CACHE_MAX` 512 and `ART_THUMB_CACHE_MAX_CHARS` 16 MiB out of
`state.svelte.js`, oldest first. Two rules the desktop does not need are
added, because its callers ask through `getArt(path)` while the phone's
templates index the map: the entry that just landed is never dropped, and
neither is one a connected `<img>` is painting — `Cover`'s `visible` action
re-arms only on a path prop change, so an evicted cover that is still mounted
would stay a disc for good. Built with the cap forced to 8 and scrolled
through eighteen screens of a 140-card Library grid, the map sat at 61 —
spared, every one of them, for being painted — and not one cover on screen
lost its image; at the shipped 512 a whole library walk runs the trim zero
times. The playlist covers need no policy at all: the new revision drops the
old ones, which are unreachable by construction.

The verification is the round. `artTally()` on the handle reports the map and
its side tables, which are module-private; seventeen probe fields carry that,
the catalog's ten session maps, the queue, the transfers and the DOM on every
step of both walks; and seven mock steps install a live listener and timer
registry in the page — by a step, not by `addScriptToEvaluateOnNewDocument`,
which the first-run block's reloads would throw away — drive two warm laps, a
baseline and nine more, assert the census, and take the registry back out so
nothing appended after this block inherits a patched platform. Installed that
late it can only see what is registered from that moment on, so its absolute
counts are small and are not asserted as a census; what is asserted is the
delta across the nine laps, and that it fires was proved by planting a
listener and an interval stranded once a lap: `grewEars` 0 → 9, `grewTicks`
0 → 9, and the step fails. As it ships, over those nine laps, the listeners
and the intervals moved by 0, the art map grew 17 against a headroom of 80
and the catalog 5 against 24, and the DOM ended smaller than it started.
`tallyTimers` is a ceiling and not a delta, and says so: every track start
schedules a 47-second recents refresh, so a walk this fast keeps a handful
pending, and making it sharp would cost a fifty-second quiet period. The
catalog maps, `tracksCache` and that recents timeout are named in ANDROID.md
as left alone on purpose — evicting a catalog entry is not safe while
`Artist.svelte` looks one up inside `untrack`. Nothing new on the phone leg:
the registry is never installed there, those three fields read −1, and
`artTally()` is a pure read.

src/mobile/Mobile.svelte

@@ -40,7 +40,7 @@
     import { lyr, loadLyrics } from "./lyrics.svelte.js";
     import Stub from "./screens/Stub.svelte";
     import { lib, loadLibrary, refreshRecents, albumById, albumsBy, watchLibrary } from "./lib.svelte.js";
-    import { art, wantArt, accentFor, applyAccent } from "./art.svelte.js";
+    import { art, artTally, wantArt, accentFor, applyAccent } from "./art.svelte.js";
     import { player, hooks, bindEvents, restoreSession, next, prev, toggle, seekSecs, playQueueAt } from "./player.svelte.js";
     import { nav, TABS, top, isRoot, bootNav, go, push, back, patch, openSheet, closeSheet, openHalf, closeHalf } from "./nav.svelte.js";
     import { loadPrefs } from "./prefs.svelte.js";
@@ -317,7 +317,7 @@
         requestAnimationFrame(() => requestAnimationFrame(() => { clearTimeout(sealTimer); sealBoot(); }));
         /* the probe handle — the desktop has __soulstream for the same reason:
            tests/mobile/smoke.mjs drives the real app through it */
-        window.__ss = { nav, top, go, push, back, openSheet, closeSheet, openHalf, closeHalf, player, lib, art, catalog, home, loadHome, lyr, loadLyrics, slsk, boot, net, resolver, streamSong, streamCatalogAlbum, sources, api, transfers, xfn: xfernote, pls, notice, importer, imp: { startFolder, startFile }, setup, openSetup, setupState, wifi: { downloadsAllowed, cellular }, next, prev, toggle, seekSecs, playQueueAt, patch, contacts, loadContacts, say, refreshRooms };
+        window.__ss = { nav, top, go, push, back, openSheet, closeSheet, openHalf, closeHalf, player, lib, art, catalog, home, loadHome, lyr, loadLyrics, slsk, boot, net, resolver, streamSong, streamCatalogAlbum, sources, api, transfers, xfn: xfernote, pls, notice, importer, artTally, imp: { startFolder, startFile }, setup, openSetup, setupState, wifi: { downloadsAllowed, cellular }, next, prev, toggle, seekSecs, playQueueAt, patch, contacts, loadContacts, say, refreshRooms };
         return () => { if (unlisten) unlisten(); };
     });
 </script>