fix(brain): move the wikilink strip into WriteNote/UpdateNote

The BrainStore is not the only door. POST /write — the HTTP path CLAUDE.md
hands to curl and scripts — calls api.WriteNote directly, so the strip
shipped one commit ago covered brain_write and capture while leaving the raw
door ungated. A gate one door wide is not a gate.

The BrainStore keeps its own call so it can still report Ref.Unlinked to the
MCP caller; running the strip twice is a no-op on content the primitive has
already cleaned.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ingestion/internal/api/handler_test.go

@@ -497,3 +497,45 @@ func TestWriteNote_RejectsClaimFieldWithoutProvenance(t *testing.T) {
 	_, statErr := os.Stat(filepath.Join(dir, "wiki/homelab/facts/no-provenance.md"))
 	assert.True(t, os.IsNotExist(statErr))
 }
+
+// The HTTP POST /write door reaches WriteNote directly, without the
+// BrainStore, so the unresolved-wikilink strip has to live in the primitive
+// or that door stays ungated.
+func TestWriteNote_UnwrapsUnresolvedWikilinks(t *testing.T) {
+	dir := t.TempDir()
+	_, err := api.WriteNote(dir, api.WriteNoteOptions{
+		Content: "# Target\n\nbody\n", Filename: "target", Wing: "a", Hall: "facts",
+	})
+	require.NoError(t, err)
+
+	rel, err := api.WriteNote(dir, api.WriteNoteOptions{
+		Content:  "See [[target]] and [[gitea-ci]].\n",
+		Filename: "src", Wing: "a", Hall: "facts",
+	})
+	require.NoError(t, err)
+
+	got, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "[[target]]")
+	assert.Contains(t, string(got), "and gitea-ci.")
+	assert.NotContains(t, string(got), "[[gitea-ci]]")
+}
+
+func TestUpdateNote_UnwrapsUnresolvedWikilinks(t *testing.T) {
+	dir := t.TempDir()
+	_, err := api.WriteNote(dir, api.WriteNoteOptions{
+		Content: "old\n", Filename: "n", Wing: "a", Hall: "facts",
+	})
+	require.NoError(t, err)
+
+	rel, _, _, err := api.UpdateNote(dir, api.UpdateNoteOptions{
+		Wing: "a", Hall: "facts", Slug: "n",
+		Content: "Related: [[secret-hygiene]].\n", Reason: "r",
+	})
+	require.NoError(t, err)
+
+	got, err := os.ReadFile(filepath.Join(dir, filepath.FromSlash(rel)))
+	require.NoError(t, err)
+	assert.Contains(t, string(got), "Related: secret-hygiene.")
+	assert.NotContains(t, string(got), "[[secret-hygiene]]")
+}