gen-tm(vue): full block-language coverage — exotic langs + custom blocks (PR #6085)

Monogram's Vue grammar only embedded ts/tsx/jsx (script), scss/less/stylus/
postcss (style), pug (template) — far short of the hand-written grammar, which
embeds via a generic `<anytag lang="X">` catch-all. Add the rest:
  - named blocks: <script lang="coffee">→source.coffee, <style lang="sass">
    →source.sass (added to their lang maps; emitRaw handles them robustly).
  - NEW customBlockEmbed map (markup config) for the data/custom-block langs on
    ANY tag: md→text.html.markdown, json→source.json, jsonc→source.json.comments,
    json5→source.json5, yaml→source.yaml, toml→source.toml, gql/graphql→
    source.graphql. So `<i18n lang="yaml">`, `<docs lang="md">`, `<gql lang=
    "graphql">` all embed correctly — Vue SFC custom blocks Monogram had no
    mechanism for.

gen-tm emits one begin/end per custom lang: the tag NAME is captured and the
close is its backreference (`</\2>`), so it's tag-agnostic; a `lang=<x>`
lookahead gates it; start-tag attrs re-tokenize via #attribute; body embeds the
mapped grammar. Emitted before the named rawText blocks. Vue-only (driven by
vue.ts data); the 5 non-Vue grammars stay byte-identical. agnostic 8/8, tsc
clean, vue-issues + vue-dropin 19/19, gen deterministic.

Author: johnsoncodehk

src/gen-tm.ts

@@ -3247,6 +3247,25 @@ function generateMarkupTm(grammar: CstGrammar, grammarName: string, scopeName: s
     };
     top.push({ include: `#raw-${tag}-ml` });
   };
+  // Custom-block embeds: ANY block tag carrying `lang="<lang>"` embeds the mapped scope in its body
+  // (the SFC custom-block convention — `<i18n lang="yaml">`, `<docs lang="md">`, `<gql lang="gql">`).
+  // One begin/end per lang: the tag NAME is captured (group 2) and the close is its BACKREFERENCE
+  // (`</\2>`), so the region is tag-agnostic. Emitted BEFORE the named rawText blocks so a data lang
+  // on a named tag still resolves here when that tag's lang map doesn't list it. The lookahead asserts
+  // `lang=<lang>` in the start tag; the start-tag attrs re-tokenize via #attribute; body → the grammar.
+  for (const [lang, scope] of Object.entries(m.customBlockEmbed ?? {})) {
+    const key = `block-${lang}`;
+    repository[key] = {
+      name: `meta.embedded.block.${L}`,
+      begin: `(${o})(${namePat})\\b(?=[^${ccClose}]*\\blang\\s*=\\s*["']?${escapeRegex(lang)}\\b)([^${ccClose}]*)(${c})`,
+      beginCaptures: { '1': { name: sOpen }, '2': { name: sName }, '3': { patterns: [{ include: '#attribute' }] }, '4': { name: sClose } },
+      end: `(${o}${slash})(\\2)\\s*(${c})`,
+      endCaptures: { '1': { name: sOpen }, '2': { name: sName }, '3': { name: sClose } },
+      contentName: scope,
+      patterns: [{ include: scope }],
+    };
+    top.push({ include: `#${key}` });
+  }
   for (const tag of m.rawText?.tags ?? []) {
     const spec = m.rawText!.embed?.[tag] ?? (tokScope(m.rawText!.token) ?? `source.${L}`);
     if (typeof spec === 'string') {

src/types.ts

@@ -95,6 +95,14 @@ export interface MarkupConfig {
   // instead map to `{ default, lang }` to pick the embed by a `lang="…"` attribute on the
   // start tag (Vue: `<script lang="ts">`→source.ts, `<style lang="scss">`→source.css.scss).
   rawText?: { tags: string[]; token: string; embed?: Record<string, string | RawEmbed> };
+  // Custom-block embeds: ANY top-level block tag (not just the named rawText ones) whose start
+  // tag carries `lang="<lang>"` embeds the mapped scope in its body — the Vue SFC custom-block
+  // convention (`<i18n lang="yaml">`→source.yaml, `<docs lang="md">`→text.html.markdown, also
+  // `<script lang="coffee">`, `<style lang="sass">`). Keyed by lang → embed scope; matches a
+  // generic tag name and closes on its backreferenced `</tag>`. Tried BEFORE the named rawText
+  // blocks, so an exotic lang wins over a named block's default (a `<script lang="coffee">`
+  // embeds source.coffee, not the script default). The common langs stay on the named blocks.
+  customBlockEmbed?: Record<string, string>;
   comment?: { open: string; close: string; token: string }; // e.g. `<!--` … `-->`
   // Void elements (`<br>`, `<img>`, `<meta>`, …) — no children, no close tag. The
   // lexer RETAGS an OPEN void-tag name from the identifier token to `voidNameToken`,