Play Framework

feat(testrunner): split DB-touching unit tests onto a single-permit lane

Stage 1 routed every U:-prefixed unit test through one N-wide parallel
gate. That breaks tests that call Fixtures.deleteDatabase() / load() or
otherwise mutate JPA state — two such tests running concurrently against
the same DB race on the table-truncate and detach each other's in-flight
entities.

TestRunner.list now ASM-walks each unit test's transitive call graph
through application classes only and tags it as DB-touching if any
reachable class references:
  * play.test.Fixtures
  * any class under play.db.*
  * any application entity (assignable to play.db.jpa.Model)

DB-touching tests get the D: prefix; pure tests stay on U:. The walk
stops at non-application boundaries (framework / library / JDK), since
application code reaches DB only through its own packages or directly
through Play's DB APIs — both caught by the marker checks. ASM scan
failures default to D: (DB-serial) so misclassification can't fall back
to the unsafe parallel path.

FirePhoque consumes both prefixes through a shared VT executor with two
gates: a parallel pureGate (N permits, default 16) and a single-permit
dbGate. The two lanes run concurrently — pure tests don't touch the
DB, so they aren't blocked by the serializing DB lane. Common gating
logic factored into submitGated() so both lanes share the acquire/
runOneUnitTest/release try-finally.

Net effect: DB-isolation preserved for fixture-driven tests, full
parallelism preserved for pure unit tests, and the two run side-by-side
instead of one waiting for the other.

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