refactor: remove implicit content sniffing and table conversion

- Split loadCSV into parseCSVString (content) and loadCSVFromPath
  (path); drop isCSV/looksLikeCsv heuristics
- Delete coerceSparkTables and markedTable label-header magic;
  plain markdown tables now render as plain tables
- Add explicit markdown role=spark-table fence syntax that converts
  pipe tables to CSV at scan time, with dice-header validation
- Map ESM-only github-slugger and csv-parse browser build to CJS in
  jest config; add content-registry tests

src/components/md-commander/stores/commandsStore.ts

@@ -2,7 +2,7 @@ import { createStore } from "solid-js/store";
 import type { MdCommanderCommand, MdCommanderCommandMap } from "../types";
 import { setupHelpCommand, clearCommand, rollCommand, trackCommand, untrackCommand, listTrackCommand } from "../commands";
 import {resolvePath} from "../../utils/path";
-import {loadCSV} from "../../utils/csv-loader";
+import {loadCSVFromPath} from "../../utils/csv-loader";
 
 const defaultCommands: MdCommanderCommandMap = {
   help: setupHelpCommand({}),
@@ -111,7 +111,7 @@ export async function loadCommandTemplatesFromCSV(
   setCommandsError(undefined);
   
   try {
-    const csv = await loadCSV<CommandTemplateRow>(resolvePath(articlePath, path));
+    const csv = await loadCSVFromPath<CommandTemplateRow>(resolvePath(articlePath, path));
 
     // 按命令分组模板
     const templatesByCommand = new Map<string, CommandTemplateRow[]>();