#9063 chore(desktop): delete the unused file-explorer and search-dialog stores

What & why

Two persisted zustand stores in apps/desktop/src/renderer/stores/ have no consumers:

Store	Lines	localStorage key
file-explorer.ts (useFileExplorerStore)	159	file-explorer-store
search-dialog-state.ts (useSearchDialogStore)	109	search-dialog-store

Grepping for the hook names and the stores/file-explorer / stores/search-dialog-state import paths finds only the files themselves and their rows in the persisted-key test registry.

As apps/desktop/AGENTS.md requires, this PR:

• moves both keys to DEAD_KEYS, so the boot sweep removes them from existing user profiles instead of leaving them there
• removes their rows from persisted-key-registry.test-data.ts

How I tested it

• apps/desktop typecheck passes
• persisted-keys tests: 12 pass, 0 fail (the registry test checks that every writer is registered and no row is stale)
• biome check is clean

Opened by the daily cleanup automation.

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Summary by cubic

Removes the unused file-explorer-store and search-dialog-store persisted zustand stores from the desktop app. Neither store had any consumers, so both localStorage keys are added to DEAD_KEYS to have the boot sweep delete them from existing user profiles, and their rows are dropped from the persisted-key registry.

Summary by CodeRabbit

• Chores
  • Previously saved file-explorer and search-dialog state is cleared during persisted-data cleanup. This affects stored folder expansion, sorting, search filters, and scope; it does not describe a new feature or change to the available search and file-browsing capabilities. The ports store remains registered.