feat(collector): rebuild link preview as package workspace

Inspect pasted links, text files and DLC containers before queue insertion and resolve supported hoster metadata without starting downloads. Group multipart files into expandable packages with size, status, availability, timestamps, filtering and stable selection. Add selected or complete transfer to Downloads while retaining entries on failed or partial handoff. Keep collector toolbar spacing consistent and show the full 1Fichier identity with its provider icon in Downloads.

tests/visual/mock-electron-api.ts

@@ -59,6 +59,8 @@ export function createVisualElectronApi(
     deleteAccount: async () => ({ accountId: null, settings: clone(fixture.snapshot.settings), accounts: clone(fixture.snapshot.accounts) }),
     addLinks: async () => ({ addedPackages: 0, addedLinks: 0, invalidCount: 0 }),
     addContainers: async () => ({ addedPackages: 0, addedLinks: 0 }),
+    inspectCollectorText: async () => clone(fixture.collector),
+    inspectCollectorContainers: async () => clone(fixture.collector),
     getStartConflicts: async () => [],
     resolveStartConflict: async (_packageId, policy) => ({
       skipped: policy === "skip",