feat(transactions): the transaction page as a receipt with context

The amount is the headline, notes come first at full width, then the
last twelve visits to the same place as a dot timeline next to the
paying account's days around it with the running balance. Fields edit in
place: j and k move, Enter opens and saves, Esc cancels, s c, s b, s t
and s s jump to classification. A matching subscription shows as a
suggestion, L links it.

src/lib/components/receipt/notes.ts

@@ -0,0 +1,67 @@
+export type Inline =
+  | { kind: "text" | "bold" | "code"; text: string }
+  | { kind: "link"; text: string; href: string };
+
+export type Block =
+  | { kind: "head"; line: Inline[] }
+  | { kind: "list"; ordered: boolean; items: Inline[][] }
+  | { kind: "para"; lines: Inline[][] };
+
+const TOKEN =
+  /\*\*([^*]+)\*\*|`([^`]+)`|\[([^\]]+)\]\((https?:\/\/[^\s)]+)\)|(https?:\/\/[^\s<>()]*[^\s<>().,;:!?'"])/g;
+const BULLET = /^\s*(?:[-*•]|(\d+)[.)])\s+(.*)$/;
+const HEAD = /^#{1,6}\s+(.*)$/;
+const LINES = /\r?\n/;
+
+export function inline(text: string): Inline[] {
+  const out: Inline[] = [];
+  let last = 0;
+  for (const match of text.matchAll(TOKEN)) {
+    const [whole, bold, code, label, href, url] = match;
+    if (match.index > last) {
+      out.push({ kind: "text", text: text.slice(last, match.index) });
+    }
+    if (bold) {
+      out.push({ kind: "bold", text: bold });
+    } else if (code) {
+      out.push({ kind: "code", text: code });
+    } else {
+      out.push({ href: href ?? url, kind: "link", text: label ?? url });
+    }
+    last = match.index + whole.length;
+  }
+  if (last < text.length) {
+    out.push({ kind: "text", text: text.slice(last) });
+  }
+  return out;
+}
+
+export function blocks(notes: string): Block[] {
+  const result: Block[] = [];
+  let open: Block | null = null;
+  for (const raw of notes.split(LINES)) {
+    const line = raw.trimEnd();
+    const head = line.match(HEAD);
+    const bullet = line.match(BULLET);
+    if (!line.trim()) {
+      open = null;
+    } else if (head) {
+      result.push({ kind: "head", line: inline(head[1]) });
+      open = null;
+    } else if (bullet) {
+      const ordered = Boolean(bullet[1]);
+      if (open?.kind !== "list" || open.ordered !== ordered) {
+        open = { items: [], kind: "list", ordered };
+        result.push(open);
+      }
+      open.items.push(inline(bullet[2]));
+    } else {
+      if (open?.kind !== "para") {
+        open = { kind: "para", lines: [] };
+        result.push(open);
+      }
+      open.lines.push(inline(line));
+    }
+  }
+  return result;
+}