Composer: smarter suggestions, links over selections, big images attached

Recipient suggestions:
- the words typed match in any order, each one the start of a word in the
  name, a nickname, the organization or the address: "jane smi" finds
  "Smith, Jane", and "globex" finds the people at Globex;
- someone written to lately ranks a little above an equal match;
- an address already in To, Cc or Bcc is no longer offered in the other
  two fields.

Pasting:
- a single web or mailto address pasted over selected words makes those
  words the link, instead of replacing them with the address;
- a pasted or dropped image over 10 MB goes in as an attachment rather
  than inline, where it would swell every reply.

No new strings.

web/src/views/compose/__tests__/editor-paste.test.tsx

@@ -0,0 +1,102 @@
+import { act } from "react";
+import { createRoot, type Root } from "react-dom/client";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { INLINE_IMAGE_MAX, RichEditor, isLinkToPaste } from "../RichEditor";
+
+(globalThis as { IS_REACT_ACT_ENVIRONMENT?: boolean }).IS_REACT_ACT_ENVIRONMENT = true;
+globalThis.ResizeObserver ??= class { observe() {} unobserve() {} disconnect() {} } as unknown as typeof ResizeObserver;
+
+/*
+ * Two things pasting into a message now does: a link pasted over selected
+ * words turns those words into the link, and an image too large to belong
+ * in the text goes in as an attachment. jsdom does no editing, so these check
+ * the command and the callback the editor reaches for.
+ */
+
+describe("what counts as a link to paste", () => {
+  it("takes one web or mailto address", () => {
+    expect(isLinkToPaste("https://example.com/a?b=1")).toBe(true);
+    expect(isLinkToPaste("http://example.com")).toBe(true);
+    expect(isLinkToPaste("mailto:[email protected]")).toBe(true);
+  });
+
+  it("leaves ordinary text and anything with spaces alone", () => {
+    expect(isLinkToPaste("see https://example.com")).toBe(false);
+    expect(isLinkToPaste("example.com")).toBe(false);
+    expect(isLinkToPaste("javascript:alert(1)")).toBe(false);
+    expect(isLinkToPaste("")).toBe(false);
+  });
+});
+
+describe("pasting into the editor", () => {
+  let host: HTMLDivElement;
+  let root: Root;
+  let onFiles: ReturnType<typeof vi.fn<(files: File[]) => void>>;
+  let exec: ReturnType<typeof vi.fn>;
+
+  beforeEach(async () => {
+    host = document.createElement("div");
+    document.body.appendChild(host);
+    root = createRoot(host);
+    onFiles = vi.fn<(files: File[]) => void>();
+    exec = vi.fn(() => true);
+    (document as unknown as { execCommand: unknown }).execCommand = exec;
+    await act(async () => {
+      root.render(<RichEditor html="<p>read the docs here</p>" onChange={() => {}} onFiles={onFiles} showToolbar={false} />);
+    });
+  });
+
+  afterEach(async () => {
+    await act(async () => root.unmount());
+    host.remove();
+  });
+
+  const editor = () => host.querySelector<HTMLElement>('[contenteditable="true"]')!;
+
+  const paste = async (data: { text?: string; html?: string; files?: File[] }) => {
+    const items = (data.files ?? []).map((f) => ({ type: f.type, kind: "file", getAsFile: () => f }));
+    const ev = new Event("paste", { bubbles: true, cancelable: true });
+    Object.defineProperty(ev, "clipboardData", {
+      value: { items, getData: (t: string) => (t === "text/plain" ? data.text ?? "" : t === "text/html" ? data.html ?? "" : "") },
+    });
+    await act(async () => editor().dispatchEvent(ev));
+    return ev;
+  };
+
+  const select = (word: string) => {
+    const text = editor().querySelector("p")!.firstChild!;
+    const i = text.textContent!.indexOf(word);
+    const r = document.createRange();
+    r.setStart(text, i);
+    r.setEnd(text, i + word.length);
+    const sel = window.getSelection()!;
+    sel.removeAllRanges();
+    sel.addRange(r);
+  };
+
+  it("turns selected words into the pasted link", async () => {
+    select("docs");
+    const ev = await paste({ text: "https://example.com/docs" });
+    expect(ev.defaultPrevented).toBe(true);
+    expect(exec).toHaveBeenCalledWith("createLink", false, "https://example.com/docs");
+  });
+
+  it("pastes a link as text when nothing is selected", async () => {
+    window.getSelection()!.removeAllRanges();
+    await paste({ text: "https://example.com/docs" });
+    expect(exec).not.toHaveBeenCalledWith("createLink", expect.anything(), expect.anything());
+  });
+
+  it("attaches a pasted image too large to sit in the text", async () => {
+    const big = new File([new Uint8Array(8)], "huge.png", { type: "image/png" });
+    Object.defineProperty(big, "size", { value: INLINE_IMAGE_MAX + 1 });
+    await paste({ files: [big] });
+    expect(onFiles).toHaveBeenCalledWith([big]);
+  });
+
+  it("keeps a normal-sized pasted image in the text", async () => {
+    const small = new File([new Uint8Array(8)], "shot.png", { type: "image/png" });
+    await paste({ files: [small] });
+    expect(onFiles).not.toHaveBeenCalled();
+  });
+});