Play Framework

feat: playDeps task with -Psync support (PF-90)

Mirrors python `play deps` and `play deps --sync`. The audit incorrectly
marked play deps as fully covered by extractPlayModules, but that only
populated modules/<name>/ — not lib/. Some workflows (Dockerfile pre-step,
deployment artifacts that ship lib/, IDE tooling that reads lib/ directly)
still need the resolved Maven deps materialized as files in app/lib/.

Behavior:
- `gradle playDeps`: copies all Gradle-resolved deps into projectDir/lib/.
  Skips files unchanged (size-based comparison). Idempotent.
- `gradle playDeps -Psync`: same as above PLUS deletes any jars in lib/
  that aren't in the current resolution. Mirrors python's --sync flag,
  which became -Dsync in DependenciesManager.

Filters the resolved set the same way playBundle does: skip framework jars
(they live at frameworkPath, not in app's lib), skip module lib jars (they
live in modules/<name>/lib via extractPlayModules), skip the destination
lib/ to avoid copying files onto themselves.

Verified against jclaw: 122 deps resolved, copied to lib/. Seeded a stale
jar, plain playDeps left it in place. -Psync correctly removed it. Second
sync run was a no-op (idempotent).

Note: in the typical Gradle workflow, lib/ doesn't actually need to be
populated — playRun/Start/etc pull deps directly from Gradle's resolved
runtimeClasspath. playDeps is for workflows that explicitly need lib/
(deployment artifacts, IDE tooling, Docker patterns inherited from the
python CLI era).