refactor: modularize auth transport and markdown

- Split auth into focused package modules for agent keys, file keys,
  signing, and post-quantum transport helpers while keeping the public
  browser_cli.auth import surface intact.
- Move transport encoding internals into a package with separate codec and
  binary-hoisting helpers, preserving browser_cli.transport compatibility.
- Extract remote TCP auth/socket helpers and serve challenge setup out of the
  runtime paths to make connection handling easier to reason about.
- Move the extension markdown extractor into a dedicated content/markdown
  folder with separate root selection, code normalization, renderer, and utils.
- Centralize CLI Rich rendering helpers for tab/window tree and table output,
  and add rendering tests for the shared builders.
- Remove local typing ignores in SDK/decorator/script plumbing and bump the
  package and extension version to 0.15.3.

extension/src/content/markdown/renderer.ts

@@ -0,0 +1,217 @@
+import { normalizeCodeBlock } from './code';
+import {
+  absoluteUrl,
+  BLOCK_TAGS,
+  collapseBlankLines,
+  escapeMarkdown,
+  escapeTableCell,
+  isNoiseElement,
+  normalizeInline,
+  normalizeText,
+} from './utils';
+
+function inlineText(node: Node): string {
+  if (node.nodeType === Node.TEXT_NODE) {
+    return escapeMarkdown(node.textContent || "");
+  }
+  if (node.nodeType !== Node.ELEMENT_NODE) return "";
+  if (isNoiseElement(node)) return "";
+
+  const el = node as HTMLElement;
+  const tag = el.tagName.toLowerCase();
+  if (tag === "br") return "\n";
+  if (tag === "img") {
+    const img = el as HTMLImageElement;
+    const src = absoluteUrl(img.getAttribute("src"), img.src);
+    if (!src) return "";
+    const alt = normalizeText(img.getAttribute("alt") || "");
+    return alt ? `![${escapeMarkdown(alt)}](${src})` : `![](${src})`;
+  }
+  if (tag === "a") {
+    const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
+    const href = absoluteUrl(el.getAttribute("href"), (el as HTMLAnchorElement).href);
+    if (!href) return text;
+    return `[${text || href}](${href})`;
+  }
+  if (tag === "code") {
+    const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
+    return text ? `\`${text.replace(/`/g, "\\`")}\`` : "";
+  }
+  if (tag === "strong" || tag === "b") {
+    const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
+    return text ? `**${text}**` : "";
+  }
+  if (tag === "em" || tag === "i") {
+    const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
+    return text ? `*${text}*` : "";
+  }
+
+  const chunks: string[] = [];
+  for (const child of el.childNodes) {
+    const rendered = inlineText(child);
+    if (!rendered) continue;
+    chunks.push(rendered);
+    if (child.nodeType === Node.ELEMENT_NODE && BLOCK_TAGS.has((child as Element).tagName.toLowerCase())) {
+      chunks.push("\n");
+    }
+  }
+  return chunks.join("");
+}
+
+function textBlock(node: Node): string {
+  return collapseBlankLines(normalizeInline(Array.from(node.childNodes).map(inlineText).join("")));
+}
+
+function preserveNodeText(node: Node): string {
+  if (node.nodeType === Node.TEXT_NODE) {
+    return node.textContent || "";
+  }
+  if (node.nodeType !== Node.ELEMENT_NODE) return "";
+
+  const el = node as HTMLElement;
+  const tag = el.tagName.toLowerCase();
+  if (tag === "br") return "\n";
+
+  const parts: string[] = [];
+  for (const child of el.childNodes) {
+    const rendered = preserveNodeText(child);
+    if (!rendered) continue;
+    parts.push(rendered);
+  }
+
+  if (["div", "p", "li"].includes(tag)) {
+    return `${parts.join("")}\n`;
+  }
+  return parts.join("");
+}
+
+function tableToMarkdown(table: Element) {
+  const rows = Array.from(table.querySelectorAll("tr"))
+    .map(row => Array.from(row.children)
+      .filter(cell => cell.tagName === "TD" || cell.tagName === "TH")
+      .map(cell => escapeTableCell(textBlock(cell)))
+    )
+    .filter(cells => cells.length > 0);
+  if (!rows.length) return "";
+
+  const widths = rows.reduce((max, row) => Math.max(max, row.length), 0);
+  const normalizedRows = rows.map(row => {
+    const next = row.slice();
+    while (next.length < widths) next.push("");
+    return next;
+  });
+
+  let headers = normalizedRows[0];
+  let bodyRows = normalizedRows.slice(1);
+  const firstRowIsBlank = headers.every(cell => !cell.trim());
+  if (firstRowIsBlank && normalizedRows.length > 1) {
+    headers = normalizedRows[1];
+    bodyRows = normalizedRows.slice(2);
+  }
+
+  const firstRow = table.querySelector("tr");
+  const thead = table.querySelector("thead");
+  const firstRowHasTh = firstRow && Array.from(firstRow.children).some(cell => cell.tagName === "TH");
+  if (!(thead || firstRowHasTh || firstRowIsBlank)) {
+    headers = new Array(widths).fill("");
+    bodyRows = normalizedRows;
+  }
+
+  const separator = new Array(widths).fill("---");
+  const lines = [
+    `| ${headers.join(" | ")} |`,
+    `| ${separator.join(" | ")} |`,
+  ];
+  for (const row of bodyRows) {
+    lines.push(`| ${row.join(" | ")} |`);
+  }
+  return lines.join("\n");
+}
+
+function listToMarkdown(list: Element, depth = 0): string {
+  const ordered = list.tagName.toLowerCase() === "ol";
+  const items: string[] = [];
+  const children = Array.from(list.children).filter(child => child.tagName === "LI");
+  children.forEach((item, index) => {
+    const marker = ordered ? `${index + 1}. ` : "- ";
+    const indent = "  ".repeat(depth);
+    const nested: string[] = [];
+    const content: string[] = [];
+
+    for (const child of item.childNodes) {
+      const childEl = child as Element;
+      if (child.nodeType === Node.ELEMENT_NODE && (childEl.tagName === "UL" || childEl.tagName === "OL")) {
+        nested.push(listToMarkdown(childEl, depth + 1));
+      } else {
+        content.push(inlineText(child));
+      }
+    }
+
+    const line = collapseBlankLines(normalizeInline(content.join("")));
+    if (line) {
+      const lineParts = line.split("\n");
+      items.push(`${indent}${marker}${lineParts[0]}`);
+      const continuationIndent = `${indent}${" ".repeat(marker.length)}`;
+      lineParts.slice(1).forEach(part => items.push(`${continuationIndent}${part}`));
+    }
+    nested.filter(Boolean).forEach(block => items.push(block));
+  });
+  return items.join("\n");
+}
+
+function blockToMarkdown(node: Node): string {
+  if (node.nodeType === Node.TEXT_NODE) {
+    return normalizeText(node.textContent || "");
+  }
+  if (node.nodeType !== Node.ELEMENT_NODE) return "";
+  if (isNoiseElement(node)) return "";
+
+  const el = node as HTMLElement;
+  const tag = el.tagName.toLowerCase();
+  if (tag === "table") return tableToMarkdown(el);
+  if (tag === "ul" || tag === "ol") return listToMarkdown(el);
+  if (el.matches(".cm-editor[data-is-code-block-view='true']")) {
+    const lines = Array.from(el.querySelectorAll(".cm-line")).map(line => {
+      const text = preserveNodeText(line);
+      return text === "\n" ? "" : text.replace(/\n$/, "");
+    });
+    const code = normalizeCodeBlock(lines.join("\n"));
+    return code ? `\`\`\`\n${code}\n\`\`\`` : "";
+  }
+  if (tag === "pre") {
+    const code = normalizeCodeBlock(preserveNodeText(el));
+    return code ? `\`\`\`\n${code}\n\`\`\`` : "";
+  }
+  if (tag === "blockquote") {
+    const content = collapseBlankLines(Array.from(el.childNodes).map(blockToMarkdown).join("\n\n"));
+    return content
+      .split("\n")
+      .map(line => line ? `> ${line}` : ">")
+      .join("\n");
+  }
+  if (/^h[1-6]$/.test(tag)) {
+    const level = Number(tag.slice(1));
+    const text = textBlock(el);
+    return text ? `${"#".repeat(level)} ${text}` : "";
+  }
+  if (tag === "p" || tag === "figcaption") {
+    return textBlock(el);
+  }
+  if (tag === "hr") {
+    return "---";
+  }
+  if (tag === "img") {
+    return inlineText(el);
+  }
+
+  const childBlocks = Array.from(el.childNodes)
+    .map(child => blockToMarkdown(child))
+    .filter(Boolean);
+  if (childBlocks.length) return collapseBlankLines(childBlocks.join("\n\n"));
+
+  return textBlock(node);
+}
+
+export function renderMarkdown(root: Element): string {
+  return collapseBlankLines(blockToMarkdown(root));
+}