refactor: consolidate block processing logic

Introduce a centralized `block-processor` and `block-scanner` to
handle markdown fenced code blocks. This replaces the previous
`inline-blocks.ts` and individual completion sources with a unified
approach that handles block stripping, directive replacement, and
metadata extraction (stats, templates, and spark tables) in a single
pass.

src/cli/completions/block-scanner.ts

@@ -0,0 +1,103 @@
+/**
+ * Shared block scanning utilities — safe for both CLI and browser.
+ *
+ * Parses fenced code blocks with attributes:
+ *   ```lang id=xxx role=xxx as=xxx
+ *
+ * - `role` dispatches to content scanners (stat, stat-template, spark-table)
+ * - `as` controls rendering (none, codeblock, md-table, md-card, md-dice)
+ * - `id` is used for cross-references (template names, file paths)
+ */
+
+import Slugger from "github-slugger";
+import type { SparkTableCompletion } from "./types.js";
+
+// ---------------------------------------------------------------------------
+// Types
+// ---------------------------------------------------------------------------
+
+export interface BlockAttrs {
+  lang: string;
+  id?: string;
+  role?: string;
+  as?: string;
+  /** Any other attributes not in the standard set */
+  extra: Record<string, string>;
+}
+
+// ---------------------------------------------------------------------------
+// Regex
+// ---------------------------------------------------------------------------
+
+/** Matches fenced code blocks with an info string (at least one attr). */
+export const FENCED_BLOCK_RE = /^```(\w*)\s+(\S.*?)\s*\n([\s\S]*?)```\s*$/gm;
+
+// ---------------------------------------------------------------------------
+// Attribute parsing
+// ---------------------------------------------------------------------------
+
+/** Parse key="value" and key=value pairs from an attribute string. */
+export function parseBlockAttrs(info: string): BlockAttrs {
+  const attrs: Record<string, string> = {};
+  const re = /(\w+)\s*=\s*("[^"]*"|\S+)/g;
+  let m: RegExpExecArray | null;
+  while ((m = re.exec(info)) !== null) {
+    attrs[m[1]] = m[2].replace(/^"|"$/g, "");
+  }
+
+  const { lang, id, role, as, ...extra } = attrs;
+  return { lang: lang || "", id, role, as, extra };
+}
+
+// ---------------------------------------------------------------------------
+// as resolution
+// ---------------------------------------------------------------------------
+
+/**
+ * Determine the effective `as` value.
+ *
+ * Defaults:
+ *   - role is set, no explicit as → "none" (strip — it's metadata)
+ *   - no role, no as → "codeblock" (keep as visible code block)
+ */
+export function resolveBlockAs(role: string | undefined, as: string | undefined): string {
+  if (as) return as;
+  if (role) return "none";
+  return "codeblock";
+}
+
+// ---------------------------------------------------------------------------
+// Spark table parsing
+// ---------------------------------------------------------------------------
+
+const DICE_RE = /^d\d+$/i;
+
+export function parseSparkTableCsv(
+  body: string,
+  filePath: string,
+  slugger: Slugger,
+): SparkTableCompletion | null {
+  const lines = body.trim().split(/\r?\n/);
+  if (lines.length < 2) return null;
+
+  const headers = lines[0].split(",").map((h) => h.trim());
+  if (headers.length < 2) return null;
+  if (!DICE_RE.test(headers[0])) return null;
+
+  const dataHeaders = headers.slice(1);
+  const slug = dataHeaders
+    .map((h) => slugger.slug(h.toLowerCase()))
+    .join("-");
+
+  const basePath = filePath.replace(/\.md$/, "");
+  const fileName = basePath.split("/").filter(Boolean).pop() || basePath;
+  const combinedSlug = `${fileName}-${slug}`;
+
+  return {
+    label: `${fileName} § ${slug}`,
+    notation: headers[0],
+    slug: combinedSlug,
+    filePath: basePath,
+    headers: dataHeaders,
+  };
+}