Group six more clusters out of web/src/lib

Takes the flat module count from 66 to 42, continuing what admin/ and
calendar/ started.

  lib/mailbox/  archiveDate, emptyFolder, folderMove, labelTree,
                mailboxName, mailboxRoute
  lib/sieve/    sieve, sieveApply, sieveFolders
  lib/input/    keyboard, swipe, touch, listSelection, dropUpload
  lib/notify/   notify, webpush, webpushEnable
  lib/sw/       swCache, swFacts, staleBuild
  lib/text/     html, markdown, text, emlName

FOUR THINGS THE FILENAMES GET WRONG, each checked by reading the file
rather than trusting what it is called:

  - appFolder is not a mailbox. It is the `ihasmail` folder in JMAP
    *Files*, where the client keeps signature images and synced settings.
    It stays flat.
  - format holds no formatting of text. It re-exports the date and clock
    formatters, so it belongs with dates/datetime, not with text/.
  - preview is the file viewer deciding what it can show without
    downloading, and source is where to point someone asking for this
    instance's AGPL source. Neither is about text.
  - notify is not Web Push. It is the tab title, the favicon badge and
    the new-mail sound -- in-app notification, which is why it sits with
    webpush rather than under sw/ with the service worker's own concerns.

threadScroll stays flat too: it decides where a conversation opens, which
is view state rather than a gesture, and input/ is honest only if
everything in it interprets something the reader did.

No behavior change. Almost every reference was on the @/ alias; eight
relative imports in files that did not move, or that moved away from a
sibling, needed rewriting by hand.

web/src/lib/input/swipe.ts

@@ -0,0 +1,90 @@
+/**
+ * What a swipe on a message row does, and what it should say it is about to do.
+ *
+ * The reader picks one action for each direction in Settings, but an action is
+ * not a fixed thing: "delete" out of Deleted Items is permanent, "report spam"
+ * inside Junk Mail is the opposite request, and "archive" while looking at the
+ * archive is nothing at all. The strip revealed behind the row has to name the
+ * thing that will actually happen, in the folder it is happening in -- a row
+ * that slides open to reveal the word "Archive" and then does nothing is worse
+ * than one that does not slide.
+ *
+ * So a direction with no meaning here resolves to `null`, and a null direction
+ * is one the row simply will not move in.
+ */
+
+export type SwipeAction = "archive" | "delete" | "spam" | "read" | "star" | "move" | "none";
+
+export interface SwipeContext {
+  /** The role of the folder on screen, where it has one. */
+  role?: string | null;
+  /** Whether the row is unread — "mark as read" is a toggle, and says so. */
+  unread: boolean;
+  starred: boolean;
+}
+
+/**
+ * Which glyph the strip shows. Named for the state it is offering rather than
+ * the setting it came from: "mark as unread" and "not spam" are the same two
+ * settings as their opposites but nothing like the same icon, and a strip that
+ * says "Not spam" beside a spam icon is asking to be misread at a glance.
+ */
+export type SwipeIcon = "archive" | "delete" | "spam" | "not-spam" | "read" | "unread" | "star" | "unstar" | "move";
+
+export interface SwipeDescriptor {
+  action: Exclude<SwipeAction, "none">;
+  label: string;
+  icon: SwipeIcon;
+  /** Which color the strip behind the row takes. */
+  tone: "danger" | "warn" | "accent" | "neutral";
+  /**
+   * Whether firing it takes the row out of the list. Those slide the rest of
+   * the way off before they fire, so the message is gone from under the finger
+   * rather than snapping home and then vanishing a frame later.
+   */
+  removes: boolean;
+  /**
+   * For the two actions that are toggles, the state this swipe sets — so the
+   * caller fires exactly what the strip promised. Read back off the row
+   * instead and a slow finger can invert it: the strip that said "Mark as
+   * read" would mark as unread if a push update landed mid-gesture.
+   */
+  on?: boolean;
+}
+
+export function describeSwipe(action: SwipeAction, ctx: SwipeContext): SwipeDescriptor | null {
+  switch (action) {
+    case "archive":
+      // Archiving out of the archive is the one no-op worth refusing outright.
+      return ctx.role === "archive" ? null : { action, label: "Archive", icon: "archive", tone: "accent", removes: true };
+    case "delete":
+      return { action, label: ctx.role === "trash" ? "Delete forever" : "Delete", icon: "delete", tone: "danger", removes: true };
+    case "spam":
+      // Nothing you wrote is spam you received, so the gesture stays inert in
+      // the two folders that hold your own mail.
+      if (ctx.role === "drafts" || ctx.role === "sent") return null;
+      return ctx.role === "junk"
+        ? { action, label: "Not spam", icon: "not-spam", tone: "warn", removes: true }
+        : { action, label: "Report spam", icon: "spam", tone: "warn", removes: true };
+    case "read":
+      return { action, label: ctx.unread ? "Mark as read" : "Mark as unread", icon: ctx.unread ? "read" : "unread", tone: "neutral", removes: false, on: ctx.unread };
+    case "star":
+      return { action, label: ctx.starred ? "Remove star" : "Add star", icon: ctx.starred ? "unstar" : "star", tone: "warn", removes: false, on: !ctx.starred };
+    case "move":
+      // The folder picker opens over the list, so the row comes home first.
+      return { action, label: "Move to…", icon: "move", tone: "accent", removes: false };
+    case "none":
+      return null;
+  }
+}
+
+/** The Settings picker's options, in the order they are offered. */
+export const SWIPE_CHOICES: ReadonlyArray<{ value: SwipeAction; label: string }> = [
+  { value: "archive", label: "Archive" },
+  { value: "delete", label: "Delete" },
+  { value: "read", label: "Mark as read / unread" },
+  { value: "star", label: "Star / unstar" },
+  { value: "spam", label: "Report spam / not spam" },
+  { value: "move", label: "Move to…" },
+  { value: "none", label: "Nothing" },
+];