fix: Correct package metadata and bring tooling to parity with the other SDKs

[razor-x]

The Ruby and Python SDKs share a common project, packaging and CI layer that
this repository never received. The codegen half was already at parity, so
this brings the language-side tooling up with it.

Packaging

• Add the description, license, homepage, keywords, support links and
  "php": "^8.0" constraint missing from composer.json, and point authors
  at Seam Labs rather than a personal address.

• Move the Tests\ PSR-4 mapping from autoload to autoload-dev, so the
  test namespace is no longer registered in consumer projects.

• Add archive.exclude so a built package ships only runtime files.
  package.json is deliberately kept, because Seam\Utils\PackageVersion
  reads it at runtime to set the seam-sdk-version header.

• Add LICENSE.txt (MIT, matching the other SDKs) and phpunit.xml.dist.

• Define the primary development tasks as Composer scripts:

  Task	Command
  Run the tests	composer test
  Lint	composer lint
  Format	npm run format
  Build the package	composer build

Continuous integration

• Replace the bespoke test.yml with check.yml, modelled on the other SDKs:
  test / lint / build / install jobs, running on pushes to main as
  well as pull requests, with job timeouts.
• Test a PHP 8.0 and 8.5 matrix, covering both ends of the supported range.
  The previous workflow pinned 8.0 only, and composer.json declared no
  constraint at all.
• Drop the SEAM_API_KEY secret, which the suite does not need, so checks now
  run on forks. The previous skip ci guard read github.event.head_commit,
  which is always null on pull_request events, so it never fired.
• Add a real PHP setup composite action (setup-php, lockfile validation,
  cached composer install). The existing action only set up Node.js, so it is
  renamed setup-node and the generate and version workflows point at it.
• Add _build.yml, which packages the library with composer build and
  uploads the archive, and an install job that requires that archive from a
  path repository and constructs a SeamClient. This also guards the
  package.json runtime dependency described above.
• Wire the archive into publish.yml, which previously created a release with
  files: ''.
• Add format.yml, so pushes are formatted with Prettier and committed. Until
  now formatting only ran as a postgenerate step, so hand-written commits
  were never formatted by CI.
• Widen Semantic Release to all branches, so the next / beta / alpha
  prerelease branches declared in .releaserc.json can actually release.
• Remove renovate.json, which used the deprecated config:base preset and
  only enabled @seamapi/types, already covered by Dependabot. Composer
  dependencies stay under manual control.
• Set CODEOWNERS to @seamapi/sdk.

Prettier was a no-op on every non-PHP file

.prettierrc.json set "parser": "php" at the top level, which forces that
parser on all files rather than setting a default. Non-PHP files were
parsed as inline HTML and written back byte-identical, so Prettier silently did
nothing for TypeScript, JSON, YAML and Markdown, and prettier --check passed
vacuously. The overrides block only adjusted options the PHP parser ignores.

The PHP parser now lives in an override on **/*.php with the plugin defaults
it was already producing, and Prettier infers the parser for everything else.
Embedded formatting is disabled for Markdown so the README examples keep the
style of the generated source. The codegen/lib changes in this PR are the
result of running the formatter over TypeScript for the first time; src/ is
unchanged.

Verification

Run locally: composer lint, composer validate --strict, npm run lint and
npm run typecheck all pass. The full build to install round trip was
exercised exactly as check.yml does it (archive, path repository,
composer install, construct a SeamClient). All workflow YAML parses and
every action and reusable-workflow reference resolves.

src/ was checked for post-8.0 syntax (readonly, enums, never,
first-class callables, intersection types) and is clean, and the tightest
floor in composer.lock is symfony/deprecation-contracts at php >=8.0.2,
which the latest 8.0.x satisfies.

Notes for review

• This title will cut a patch release. That is intentional, since the
  corrected package metadata and the autoload-dev change are consumer
  visible. Retitle to chore: before merging if you would rather not release.
• PHP 8.0 is EOL. Testing it is the honest consequence of the ^8.0
  constraint. Raising the floor is a one-line change but breaks existing
  consumers.
• PHPUnit is pinned at ^9.5, a 2022 release, and phpunit.xml.dist sets
  failOnWarning="true". If PHP 8.5 surfaces deprecations through its error
  handler, that leg will go red and the fix is a manual PHPUnit bump.

Deferred to a follow-up: wiring @seamapi/fake-seam-connect into the test
harness and growing the suite beyond its single file, PHPStan and an enforced
phpcs ruleset, a devcontainer, .php-version, and a README rebuild with
badges and a table of contents.

🤖 Generated with Claude Code

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