Play Framework

docs: divergence audits — Joda removal, samples-and-tests, virtual threads (PF-84 part 2)

Refresh manual content to match the 1.12 fork's runtime model and remove
references to artifacts that no longer ship with the framework.

Files touched:

* asynchronous.textile — replaced the "fixed thread pool / N+1 sizing"
  framing with the virtual-threads model (JEP 491). Suspend/await is still
  presented as the way to drop a request out of context, but the
  motivation is no longer "platform threads are scarce." Removed the
  @samples-and-tests/chat@ tip.
* jobs.textile — added a one-paragraph note that scheduled and triggered
  jobs run on virtual threads and that @play.jobs.pool@ /
  @play.threads.virtual*@ are gone.
* production.textile — added "JDK requirement" (Java 25+, --release 25)
  and "Deployment model" (stand-alone Netty, no servlet/WAR path) right
  after the intro, with cross-links to httpserver.textile and
  deployment.textile.
* dependency.textile — added a short subsection on the @playCoreDependencies@
  chain resolver (PF-83): local @framework/lib/@ first, Maven Central
  fallback, no manual jar pre-seeding required for new framework deps.
* test.textile — refreshed the testrunner section to use @play test myapp@
  / @play auto-test myapp@ wording, fixed the module name (@testrunner@,
  not @test-runner@), and clarified that auto-test uses Selenium/Firephoque.
* guide1.textile — replaced the @samples-and-tests/yabe@ pointer with a
  generic "build it from scratch" note (the directory was removed in
  cf494a7ba).
* guide12.textile — replaced the @samples-and-tests/yabe@ starting-point
  pointer with a cross-link back to guide1.

Verification self-checks (all clean for owned files):
* No Joda references in controllers/model/validation/i18n.
* No samples-and-tests / just-test-cases hits in any owned file or
  asynchronous.textile / test.textile.
* No instructional WAR / JEE / app server hits (the remaining matches are
  legitimate: log-level @WARN@ in jobs/asynchronous, "no servlet/WAR
  path" in production).
* No @Play 1.5@ / @1.5.x@ version-string hits in owned files.

secure.textile was left alone — it does not currently discuss password
storage, so the PBKDF2 mention was not applicable. controllers/model/
validation/i18n had no Joda references to migrate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>