Add facetName tests

Also:
- Add a default categories: [] to collections if they lack it
- Add title to some categories to be able to properly assert their title
- Fix permalinks for all posts in the fixture
- Update the top comment-block to reflect the changes
- Remove some redundant checks
- Remove DOM-coupling and specific checks for DOM structure

Author: scriptype

AGENTS.md

@@ -6,6 +6,7 @@
 - For multiple expressions with logical operators (&&, ||), break lines after each operator
 - No trailing whitespace at the end of lines
 - In multiline comments, add blank lines between logical points for readability
+- Respect existing indentation style when editing files (maintain consistency with surrounding code)
 
 ## Test Assertions Formatting
 - Assertion function call on one line (e.g., `t.ok(`, `t.equal(`, `t.notOk(`)