feat(organizations): add Organizations resource, Page<T>, and list-options pattern

[fbarrento]

Closes #3.

Summary

First paginated resource. Establishes the Page<T> + List{Resource}Options + Saloon BaseResource patterns that every subsequent resource (#4–#9) will reuse.

Generic infrastructure

• Data\Page<T> — generic readonly page with data, nextCursor, prevCursor, size. Implements IteratorAggregate (yields items) and JsonSerializable. hasMore() reflects nextCursor !== null.
• Data\Organization — readonly DTO, hydrated from a JSON:API resource object via Organization::from(). Throws on missing required keys; dates parsed to DateTimeImmutable. Implements JsonSerializable.
• Data\ListOrganizationsOptions — readonly DTO with size + cursor. toQuery() emits Forge's page[size] / page[cursor] shape. Spec doesn't define sort or filter[] on /orgs, so the DTO matches.

Saloon layer

• Resources\OrganizationsResource (extends Saloon\Http\BaseResource) — all(?Options): Page<Organization> for one HTTP call; iterate(?Options): Generator<Organization> for lazy auto-pagination following meta.next_cursor until null.
• Resources\OrganizationResource — get(): Organization for a single org by slug.
• Requests\Organizations\GetOrganizations (GET /orgs) and GetOrganization (GET /orgs/{slug}).

Forge facade

• $forge->organizations() → OrganizationsResource
• $forge->organization($slug) → OrganizationResource
• The default-org constructor property is renamed defaultOrganization to free the organization() method name. README + Forge tests updated.

Tests (ortto-sdk style)

One test file per source class, mirroring src/, all under tests/Unit/:

• Data/{Page,Organization,ListOrganizationsOptions}Test.php
• Requests/Organizations/{GetOrganization,GetOrganizations}Test.php
• Resources/{Organization,Organizations}ResourceTest.php
• The 35-test ForgeTest.php from the previous PR is split into smaller per-source-class files:
  • tests/Unit/ForgeTest.php (constructor + factories + accessor types, ~16 tests)
  • tests/Unit/Requests/Me/GetMeTest.php (5 happy-path + 13 error-mapping)
  • tests/Unit/Exceptions/ValidationExceptionTest.php (3 tests)
  • tests/Unit/Exceptions/RateLimitExceptionTest.php (2 tests)

Fixtures

Recorded against the real Forge API (no hand-crafted bodies), committed under tests/Fixtures/Saloon/organizations/{list,get}.json. ForgeFixture now redacts org slugs in both attributes.slug (JSON-key pass) and links.self.href URLs (regex pass that handles both / and JSON-escaped \/), mapping consistently so attributes.slug=test-org-1 always aligns with .../orgs/test-org-1.

Notes

• The iterate() pagination control-flow test uses a sequence of MockResponse::make() (the only deterministic way to test cursor-following without making the test depend on the user's exact org count). All shape assertions still go through the real recorded fixture.

Test plan

• composer test green locally (Pint, Rector, PHPStan max, Pest at --exactly=100, 76/76 tests)
• CI matrix green across P{8.4,8.5} × {ubuntu, macos, windows} × {prefer-lowest, prefer-stable}
• Confirm fixtures contain no real slugs anywhere (already verified locally — slugs replaced in both attribute and URL contexts)

🤖 Generated with Claude Code