feat(notes): show line numbers on non-markdown file views

CSS counters on the per-line spans, scoped to .code-file so fenced
blocks inside notes stay untouched. The gutter width adapts to the
file's line count and numbers are excluded from text selection.

src/hooks/useMarkdown.hook.spec.ts

@@ -0,0 +1,42 @@
+import { describe, expect, it, vi } from "vitest"
+
+vi.mock("@/data/data", () => ({
+  data: {},
+  generateId: (type: string, id: string) => `${type}-${id}`
+}))
+
+import { renderCodeFile } from "@/hooks/useMarkdown.hook"
+
+describe("renderCodeFile", () => {
+  it("wraps highlighted files in a code-file container with a sized gutter", async () => {
+    const html = await renderCodeFile({
+      rawContent: "const a = 1\nconst b = 2\n",
+      lang: "typescript",
+      filename: "example.ts"
+    })
+
+    expect(html).toContain('<div class="code-file"')
+    expect(html).toContain("--line-number-width:1ch")
+    expect(html.match(/class="line"/g)).toHaveLength(2)
+  })
+
+  it("wraps each line of unknown-language files in line spans", async () => {
+    const html = await renderCodeFile({
+      rawContent: "line one\nline <two>\n",
+      lang: null
+    })
+
+    expect(html).toContain('<span class="line">line one</span>')
+    expect(html).toContain('<span class="line">line &lt;two&gt;</span>')
+    expect(html.match(/class="line"/g)).toHaveLength(2)
+  })
+
+  it("sizes the gutter for files with many lines", async () => {
+    const html = await renderCodeFile({
+      rawContent: Array.from({ length: 120 }, (_, i) => `line ${i}`).join("\n"),
+      lang: null
+    })
+
+    expect(html).toContain("--line-number-width:3ch")
+  })
+})

src/hooks/useMarkdown.hook.ts

@@ -421,10 +421,22 @@ export const renderCodeFile = async ({
 }): Promise<string> => {
   await useShikiji()
   const heading = filename ? `# ${filename}\n\n` : ""
+  // Drop the trailing newline so the final empty line isn't numbered.
+  const lines = rawContent.replace(/\n$/, "").split("\n")
+  // Sized gutter so line numbers stay right-aligned past 3 digits.
+  const wrapper = `<div class="code-file" style="--line-number-width:${String(lines.length).length}ch">`
   if (lang !== null) {
-    return renderMarkdown(`${heading}\`\`\`\`${lang}\n${rawContent}\n\`\`\`\``)
+    const rendered = renderMarkdown(
+      `${heading}\`\`\`\`${lang}\n${lines.join("\n")}\n\`\`\`\``
+    )
+    // Shikiji always appends an empty line span; drop it so it isn't numbered.
+    return `${wrapper}${rendered.replace('\n<span class="line"></span></code>', "</code>")}</div>`
   }
-  return `${renderMarkdown(heading)}<pre><code>${md.utils.escapeHtml(rawContent)}</code></pre>`
+  // Mirror Shikiji's per-line spans so the line-number CSS applies uniformly.
+  const code = lines
+    .map((line) => `<span class="line">${md.utils.escapeHtml(line)}</span>`)
+    .join("\n")
+  return `${wrapper}${renderMarkdown(heading)}<pre><code>${code}</code></pre></div>`
 }
 
 export const markdownBuilder = (defaultPrefix?: Ref<string> | string) => {