test(ui): clear localStorage between component tests

A test file does not get its own origin. `@vitest/browser-playwright`
opens one BrowserContext per session and runs several files in it, one
after another, so everything a component persists survives from file to
file. `track-list` restores its sort in `connectedCallback` and
`aria-tail.test.ts` activates the Title column header, so any file that
mounts a track list later in that tab opens sorted by title — where
`track-11` precedes `track-3`, which is #138's failure exactly.

Nothing about it is specific to that pair: a probe that throws when a
test starts with a non-empty `localStorage` failed 24 test-starts in one
full run (11 with the two sort keys, 8 with `cover-grid-size`, 5 with
`track-list-column-widths`) and cascaded into 248 failures. Which files
share a tab, and in what order, changes run to run, which is the whole
of why this reads as a 1-in-3 flake and passes in isolation.

The clear belongs in `setup.ts` rather than in the specs that write,
because the spec that reads is never the one that knows — and it is
safe for the same reason the leak exists: files within a session are
sequential, so it cannot wipe storage a concurrent file is using.

The spec now also states the order it asserts rather than inheriting a
default, and checks the row it is about to double-click carries the path
it expects, so a stray sort fails by naming itself instead of as an
off-by-eight file path.

Closes #138

CLAUDE.md

@@ -262,6 +262,26 @@ real store code. A binding carries an **ID**, not a name
 `yellowjacket/backend/home.Service.GetShelves`), so the fake derives
 that map from the generated tree rather than writing it down.
 
+**A test file does not get its own origin, so `setup.ts` clears
+`localStorage` between tests.** `@vitest/browser-playwright` opens one
+BrowserContext per session and runs several files in it one after
+another, so everything a component persists — the track list's sort and
+column widths, the cover size, `now-playing`'s scroll mode — is still
+there when the next file mounts the same component. Which files share a
+tab, and in what order, changes run to run, so the symptom is a spec
+that fails about one test in three and passes every time it is run on
+its own: #138 cost three scheduled runs, one of them a PR whose diff
+held no frontend code at all. Measured on the build before the fix, a
+single full run started **24** tests with storage already set. Two
+things follow. The clear is safe precisely because the leak is
+sequential — files in a session do not overlap, so it cannot wipe
+storage a concurrently-running file is in the middle of using — and it
+belongs in `setup.ts` rather than in the specs that write, because the
+spec that *reads* is never the one that knows. And a spec whose
+assertion depends on an order still **states that order** rather than
+inheriting a default, or the next change to a default is the same
+mystery again.
+
 **`frontend/bindings/` is generated by `wails3`, not `go generate`**, so
 the pre-commit codegen check does not cover it. `make bindings-check`
 (~3.5 s warm, ~20 s on a cold build cache, also a pre-commit hook)