Improve E2E Magazine

Had to add dates to posts so e2e test can properly check facet rendering

shorten some paragraphs

add more coding conventions to agents

add assertions about facets page of each collection. make sure unused
facets are not rendered anywhere, and used facets and all of their
values are rendered exactly once both in collection page and the
collection's facet page (/by)

Author: scriptype

AGENTS.md

@@ -2,9 +2,10 @@
 - Avoid semicolons unless it's absolutely necessary
 - Always use block statements even if it could be a one-liner
 - Always use curly braces {} for control structures (if, for, while, etc.), even if the body is a single statement
-- Keep lines shorter than 80 columns
+- Keep lines shorter than 80 columns (including comments)
 - 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
 
 ## Test Assertions Formatting
 - Assertion function call on one line (e.g., `t.ok(`, `t.equal(`, `t.notOk(`)
@@ -27,4 +28,9 @@
 - Focus on meaningful differences: testing the same logic with different data types (strings vs numbers) is redundant; test different behavior patterns instead
 - Include edge cases and boundary conditions (empty inputs, zero values, falsy values, etc.)
 - Remove tests that are functionally identical to existing ones, even if they test the same function in different scenarios
-- Prioritize tests that demonstrate unexpected or complex behaviors over tests that verify basic functionality with different data types
+- Prioritize tests that demonstrate unexpected or complex behaviors over tests that verify basic functionality with different data types
+
+## DOM Element Assertions
+- Use `.length === 1` to assert an element is rendered exactly once (strict, single element expectation)
+- Use `.length !== 0` to assert elements exist but allow multiple (when multiple are expected)
+- Never use `.length > 0` as it's ambiguous about whether one or multiple elements are expected