Complete files UI rewiring to the deployed api surface; expose mimeClass

page.tsx now calls the real backend: GET /files with groupId/name/mimeClass/
cursor/limit (origin filter dropped — the api has no origin param), shares
tracked as ShareCreated (revoke by id), retention mapped to the orthogonal
legalHold model, downloads by item.name, samples reshaped to the wire
contract.

GroupFile gains mimeClass (the indexed coarse class the row icon and the
filter depend on): core contract, service row mapper, parseGroupFile guard,
test fixture, UI types — one vocabulary end to end. parseGroupFile's roomId
becomes null-tolerant to match direct-upload rows (mapping input stays
strict).

Verified: core build clean, api typecheck 0 errors + group-files 22/22,
web typecheck 0 errors.

apps/api/src/group-files/group-files.service.ts

@@ -160,6 +160,7 @@ function rowToGroupFile(row: ArchiveRow, libraryUrl: (resourceId: string) => str
     origin,
     name: row.original_name,
     mimeType: row.mime,
+    mimeClass: row.mime_class as MimeClass,
     sizeBytes: safeNumber(row.byte_size),
     checksum: { algorithm: "sha256", value: row.sha256 },
     createdAt: iso(row.created_at),

apps/api/src/group-files/group-files.test.ts

@@ -135,6 +135,7 @@ describe("group-files runtime validation (shared contracts)", () => {
       origin: { kind: "matrix", mxcUri: "mxc://example.org/x" },
       name: "clip.mp4",
       mimeType: "video/mp4",
+      mimeClass: "video",
       sizeBytes: 12,
       checksum: { algorithm: "sha256", value: hex64("z") },
       createdAt: "2026-01-02T03:04:05Z",

apps/api/src/group-files/group-files.validation.ts

@@ -216,12 +216,13 @@ export function parseGroupFile(value: unknown, field = "item"): GroupFile {
     id: stringField(value, "id", `${field}.id`),
     workspaceId: stringField(value, "workspaceId", `${field}.workspaceId`),
     groupId: stringField(value, "groupId", `${field}.groupId`),
-    roomId: requireRoomId(value.roomId, `${field}.roomId`),
+    roomId: value.roomId === undefined || value.roomId === null ? null : requireRoomId(value.roomId, `${field}.roomId`),
     senderId: requireMxid(value.senderId, `${field}.senderId`),
     eventId: eventId === undefined || eventId === null ? null : eventId,
     origin,
     name: stringField(value, "name", `${field}.name`),
     mimeType: stringField(value, "mimeType", `${field}.mimeType`),
+    mimeClass: enumField(value, "mimeClass", MIME_CLASSES, `${field}.mimeClass`),
     sizeBytes: integerField(value, "sizeBytes", `${field}.sizeBytes`),
     checksum: { algorithm: "sha256", value: requireSha256(checksum.value, `${field}.checksum.value`) },
     createdAt: isoField(value, "createdAt", `${field}.createdAt`),