fix(nav): the address keeps what the app rewrites around it (review round 3)

- The Feed press over a live search ends only the search: the feed's own view stays named.
- Leaving a search steps back only off an entry the app pushed (_ytOwn); one a link or a reload
  opened is cleared in place, also where the Navigation API is missing.
- useUrlMirror rewrites a changed view through replaceView, so a reload's overlay marks go; its
  first write and its landing writes keep them for an overlay that reopens.
- Files and Playlists: a box emptied and filled again settles at once, never naming the ended search.
- Playlists: a linked player is scoped to the playlist the store started with, and only the rail's
  own move to the first playlist is no pick.
- Contract: writer objects are scanned to their matching brace, a computed or shorthand key is
  refused, and every useHistorySubview call hands a named definition.
- Lint: playwright/no-skipped-test also refuses fixme (gate snapshot regenerated).
- FEED_DEFAULT_SORT at the three remaining sites; linkedNotListed says to search by name.

frontend/eslint.config.js

@@ -898,7 +898,8 @@ export default tseslint.config(
     plugins: { playwright },
     rules: {
       "playwright/no-focused-test": "error",
-      "playwright/no-skipped-test": "error",
+      // fixme too: a test Playwright never runs, which the bookmark net would still count.
+      "playwright/no-skipped-test": ["error", { disallowFixme: true }],
     },
   },
   {