test: cover post-merge gaps in utils, services, and hooks

Adds specs for the files added or modified in the recent merge that
weren't yet covered: oauthReturnPath, withATProtoImages, link,
displayLanguage, and the useGitHubContent / useImageUpload /
useNoteFreshness hooks. Locks in the new pullLatest contract
({raw, failureStatus}) and the fetchLatestSha branch semantics
(ok/unauthorized/offline).

src/modules/atproto/withATProtoImages.spec.ts

@@ -0,0 +1,55 @@
+import { describe, expect, it } from "vitest"
+
+import { withATProtoImages } from "./withATProtoImages"
+
+const PDS = "https://pds.example.com"
+const DID = "did:plc:abc123"
+
+describe("withATProtoImages", () => {
+  it("rewrites a bafkrei CID image to a getBlob URL", () => {
+    const out = withATProtoImages(
+      "![cover](bafkreigh2akiscaildc7r4apx2t6q4t6n6kxjpw3xhqxkfvvbprdaezz4i)",
+      { pds: PDS, did: DID }
+    )
+
+    expect(out).toContain(
+      `${PDS}/xrpc/com.atproto.sync.getBlob`
+    )
+    expect(out).toContain("did=did%3Aplc%3Aabc123")
+    expect(out).toContain(
+      "cid=bafkreigh2akiscaildc7r4apx2t6q4t6n6kxjpw3xhqxkfvvbprdaezz4i"
+    )
+  })
+
+  it("preserves the alt text", () => {
+    const out = withATProtoImages("![my cover](bafkreiabc)", {
+      pds: PDS,
+      did: DID
+    })
+    expect(out).toMatch(/!\[my cover\]/)
+  })
+
+  it("rewrites multiple images in one pass", () => {
+    const md = "![a](bafkreiaaa) and ![b](bafkreibbb)"
+    const out = withATProtoImages(md, { pds: PDS, did: DID })
+
+    expect(out.match(/com\.atproto\.sync\.getBlob/g)).toHaveLength(2)
+    expect(out).toContain("cid=bafkreiaaa")
+    expect(out).toContain("cid=bafkreibbb")
+  })
+
+  it("leaves regular image URLs untouched", () => {
+    const md = "![pic](https://example.com/a.png)"
+    expect(withATProtoImages(md, { pds: PDS, did: DID })).toBe(md)
+  })
+
+  it("leaves CIDs that don't match the bafkrei prefix untouched", () => {
+    const md = "![x](sha256-abc123)"
+    expect(withATProtoImages(md, { pds: PDS, did: DID })).toBe(md)
+  })
+
+  it("preserves an empty alt text", () => {
+    const out = withATProtoImages("![](bafkreiabc)", { pds: PDS, did: DID })
+    expect(out).toMatch(/^!\[\]/)
+  })
+})