refactor: remove as= override and render data-spark at runtime

- Drop resolveBlockAs and the as= attribute; scanDoc now switches
  directly on role and warns on unknown roles instead of silently
  stripping
- md-table derives data-spark from its loaded CSV via
  parseSparkTableCsv; delete injectSparkDirectives and the second
  registry pass so pathIndex is exactly scanDoc output
- Align spark-table dice header regex with isSparkTableHeader

src/cli/completions/variable-system.test.ts

@@ -28,7 +28,7 @@ jest.mock("github-slugger", () => {
 // ---------------------------------------------------------------------------
 
 import { parseDeclareCsv } from "./declare-parser";
-import { parseBlockAttrs, resolveBlockAs } from "./block-scanner";
+import { parseBlockAttrs } from "./block-scanner";
 import { evaluateExpression, exprValueToString } from "../../components/journal/variable-expression";
 import {
   initReactivity,
@@ -220,10 +220,9 @@ describe("parseBlockAttrs", () => {
     // parseBlockAttrs receives the info string AFTER the lang.
     // The lang is extracted from the fenced block regex capture group
     // and applied separately in content-registry.
-    const attrs = parseBlockAttrs("id=stats role=declare as=none");
+    const attrs = parseBlockAttrs("id=stats role=declare");
     expect(attrs.id).toBe("stats");
     expect(attrs.role).toBe("declare");
-    expect(attrs.as).toBe("none");
   });
 
   test("parses quoted values", () => {
@@ -242,7 +241,6 @@ describe("parseBlockAttrs", () => {
     expect(attrs.lang).toBe("");
     expect(attrs.id).toBeUndefined();
     expect(attrs.role).toBeUndefined();
-    expect(attrs.as).toBeUndefined();
   });
 
   test("handles empty info string (lang extracted separately)", () => {
@@ -252,28 +250,8 @@ describe("parseBlockAttrs", () => {
   });
 });
 
-describe("resolveBlockAs", () => {
-  test("returns explicit as value", () => {
-    expect(resolveBlockAs("declare", "codeblock")).toBe("codeblock");
-  });
-
-  test("defaults to none when role is set", () => {
-    expect(resolveBlockAs("declare", undefined)).toBe("none");
-    expect(resolveBlockAs("file", undefined)).toBe("none");
-  });
-
-  test("defaults to md-table for spark-table role", () => {
-    expect(resolveBlockAs("spark-table", undefined)).toBe("md-table");
-  });
-
-  test("defaults to codeblock for tag role", () => {
-    expect(resolveBlockAs("tag", undefined)).toBe("codeblock");
-  });
-
-  test("defaults to codeblock when no role and no as", () => {
-    expect(resolveBlockAs(undefined, undefined)).toBe("codeblock");
-  });
-});
+// Role behavior is covered by the scanDoc tests in
+// src/cli/content-registry.test.ts.
 
 // ---------------------------------------------------------------------------
 // variable-expression