Store category prompts as EXACT split legacy text, no boilerplate

The per-category prompt editor showed English machine boilerplate
("Role: description. Build JSON …", schema intro, {{var}} context lines)
because seed/sync baked the render framing into categories.prompt. Now the
stored overlay is exactly the legacy wp_product_categories.sql content,
split into the three sections a user would type themselves:

  --- Title ---        Slovenian naming formula
  --- Description ---  legacy <H2>/<p>/<ul> body structure
  --- Meta ---         legacy metaDescription instruction

Schema, role framing, and Name/Description/Category/Attrs product context
stay render-time only (system template + ensureCategoryEnhanceUserContext),
where they already existed.

- SplitLegacyCombinedEnhancePrompt: non-legacy input now returns "" —
  categories without seed/legacy content get their override CLEARED
  (company default) instead of being stuffed with the canonical template
  (e.g. parent categories like "Bela tehnika" absent from the SQL).
- CategoryEnhancePromptNeedsRepair flags stored boilerplate ("parsed as
  JSON", "Build JSON", retired Attributes section) so Sync rewrites old
  data to the clean shape; repair supports clearing (prompt = '{}').
- seed-a1 apply-category-prompts skips instead of writing template text.
- Web editor compose stores only the user's section text: empty sections
  keep bare markers, default bodies and the default preamble are never
  persisted (DEFAULT_SECTION_BODIES removed).
- Verified locally: apply rewrote 238 A1+Demo categories (216 exact
  splits, 22 cleared), zero boilerplate matches in DB, idempotent re-run
  (would_update=0).

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

apps/api/internal/aiprompts/kinds_test.go

@@ -43,17 +43,16 @@ func TestCategoryEnhancePromptNeedsRepair(t *testing.T) {
 	if CategoryEnhancePromptNeedsRepair("") {
 		t.Fatal("empty should not need repair")
 	}
-	if CategoryEnhancePromptNeedsRepair(CategoryEnhanceUserTemplate) {
-		t.Fatal("canonical template should be idempotent")
-	}
-	if CategoryEnhancePromptNeedsRepair("  " + CategoryEnhanceUserTemplate + "\n") {
-		t.Fatal("whitespace-trimmed canonical should be idempotent")
+	// A STORED copy of the built-in template is boilerplate pollution — repair
+	// clears it so the category falls back to the company default.
+	if !CategoryEnhancePromptNeedsRepair(CategoryEnhanceUserTemplate) {
+		t.Fatal("stored canonical template text should need repair (cleared to default)")
 	}
 	legacy := `Ustvari nov opis\n<H2>foo</H2>\nAttrs missing`
 	if !CategoryEnhancePromptNeedsRepair(legacy) {
 		t.Fatal("legacy HTML prompt should need repair")
 	}
-	// Per-category sectioned overlay (Slovenian rules) must not force re-repair.
+	// Per-category sectioned overlay (pure Slovenian rules) must not force re-repair.
 	split := SplitLegacyCombinedEnhancePrompt(`GPT predloga:
 <name>{Napiši tip izdelka}</name>
 <metaDescription>{140 znakov}</metaDescription>
@@ -61,6 +60,9 @@ func TestCategoryEnhancePromptNeedsRepair(t *testing.T) {
 	if CategoryEnhancePromptNeedsRepair(split) {
 		t.Fatal("sectioned split overlay should be idempotent")
 	}
+	if CategoryEnhancePromptNeedsRepair("  " + split + "\n") {
+		t.Fatal("whitespace-trimmed split overlay should be idempotent")
+	}
 }
 
 func TestBuiltInProductEnhanceUsesSharedUserTemplate(t *testing.T) {