fill D2-7: test nil excerpt/author/language absent from frontmatter

SPECGAPS.md

@@ -144,7 +144,7 @@ All reconciled to follow code. Specs must be self-consistent and match code.
 | ~~D2-4~~ | ~~UniqueScriptSlug dedup~~ | ~~script.allium:115~~ | **Resolved:** test added asserting two scripts with same title produce unique slugs (`dup-slug` → `dup-slug-2`) |
 | D2-5 | ~~FrontmatterRoundtrip invariant~~ | post.allium:223 | **Resolved:** test added — creates post with all fields, publishes, parses file back via `Frontmatter.parse_document`, asserts every field (id, title, slug, excerpt, status, author, language, doNotTranslate, templateSlug, tags, categories, createdAt, updatedAt, publishedAt, body) matches the published DB record |
 | ~~D2-6~~ | ~~SidecarRoundtrip invariant~~ | ~~media.allium:198~~ | **Resolved:** 2 tests added — full roundtrip (write sidecar, parse via `Sidecar.parse_document/1`, assert all fields match DB) + nil conditional fields absent from parsed sidecar |
-| D2-7 | ConditionalPostFields: nil fields absent from frontmatter | frontmatter.allium:398 | Write test: post with nil excerpt/author/language → fields not in file |
+| ~~D2-7~~ | ~~ConditionalPostFields: nil fields absent from frontmatter~~ | frontmatter.allium:398 | **Resolved:** test added — post with nil excerpt/author/language → those fields absent from published file, 3 refute assertions |
 | D2-8 | ConditionalMediaFields: nil fields absent from sidecar | frontmatter.allium:417 | Write test: media with nil title/alt → fields not in sidecar |
 | D2-9 | max_posts_per_page 1..500 constraint | metadata.allium:75-77 | Write test: values outside range rejected |
 | D2-10 | SandboxedExecution: restricted capabilities blocked | script.allium:84-88 | Write test: filesystem/process/package loading blocked |

test/bds/posts_test.exs

@@ -256,6 +256,31 @@ defmodule BDS.PostsTest do
     refute file_contents =~ "doNotTranslate"
   end
 
+  test "publish_post omits nil excerpt, author, language from frontmatter", %{
+    project: project,
+    temp_dir: temp_dir
+  } do
+    assert {:ok, post} =
+             BDS.Posts.create_post(%{
+               project_id: project.id,
+               title: "Nil Optional Fields",
+               content: "body"
+             })
+
+    assert is_nil(post.excerpt)
+    assert is_nil(post.author)
+    assert is_nil(post.language)
+
+    assert {:ok, published} = BDS.Posts.publish_post(post.id)
+
+    full_path = Path.join(temp_dir, published.file_path)
+    file_contents = File.read!(full_path)
+
+    refute file_contents =~ "excerpt:"
+    refute file_contents =~ "author:"
+    refute file_contents =~ "language:"
+  end
+
   test "publish_post deletes old file when file path changes", %{
     project: project,
     temp_dir: temp_dir