Harden the Paginate constructor against missing/invalid config

[pcbeingused333]

Two ways Perron::Paginate.new crashes on config that a caller can realistically hand it.

1. base_path omitted → NoMethodError

base_path: is an optional keyword (base_path: nil), but omitting it breaks next / previous once the collection has more than one page:

Perron::Paginate.new((1..10).to_a, page: 1, per_page: 5).next
# => NoMethodError: undefined method `sub' for nil

previous from page 2 also returns nil even though previous? is true. Fixed by defaulting base_path to "/" (and coercing an explicit nil), so an omitted base_path yields root-relative paths (/page/2/, /).

2. non-positive per_page → cryptic errors

config.pagination.per_page has no default (only path_template is set in Resource::Configuration), so an unconfigured collection reaches Paginate.new(per_page: nil):

per_page	current behaviour
nil	TypeError: nil can't be coerced into Float
0	FloatDomainError: Infinity
negative	ArgumentError: min argument must be smaller than max argument (from clamp)

Now validated up front: ArgumentError: per_page must be a positive integer, got nil.

Tests

Four new cases in paginate_test.rb (next/previous with base_path omitted and explicitly nil; per_page of 0 / -5 / nil / 2.5). All fail on main. bundle exec rake is green (405 runs, 0 failures; standardrb clean).

🤖 Generated with Claude Code

[pcbeingused333]

CI is on action_required (fork gate) — could you press "Approve and run workflows"? Verified locally with bundle exec rake (Docker, Ruby 3.4): 404 runs, 0 failures, standardrb clean. The three new tests fail on main (NoMethodError: undefined method 'sub' for nil, and previous returning nil).

[pcbeingused333]

Updated: added per_page validation (an unconfigured pagination.per_page currently reaches Paginate.new(per_page: nil) → TypeError). Still one file of behaviour + one test file. bundle exec rake green — 405 runs, 0 failures, standardrb clean. CI is still action_required (fork gate) if a maintainer can approve the run.