Play Framework

[PF-37..PF-53] Audit follow-ups: clear all 17 post-migration findings

Closes the remaining audit tickets from the multi-agent post-migration
review (PF-37..PF-43) and the external Codex review (PF-44..PF-53).
299/299 unit tests pass.

Protocol correctness:
- PF-37 StreamChunkAggregator: strip only the `chunked` token from
  Transfer-Encoding so coexisting codings (e.g. gzip) survive aggregation
- PF-38 PlayHandler: install Netty's WebSocketFrameAggregator after the
  handshake so fragmented WS messages are reassembled before reaching
  the controller
- PF-39 PlayHandler: server-initiated close now writes a
  CloseWebSocketFrame with status 1000 via the handshaker; peers no
  longer observe 1006 ("Abnormal Closure")
- PF-40 LazyChunkedInput: stop pre-encoding chunked frames; under
  Netty 4, HttpResponseEncoder auto-frames ByteBufs in chunked state and
  the manual `len\r\n...\r\n` wrappers double-encoded the wire stream.
  The terminator is now emitted by LastHttpContent.EMPTY_LAST_CONTENT
- PF-47 FileService: malformed Range headers (missing `bytes=` prefix,
  non-numeric values) no longer NPE inside ChunkedWriteHandler;
  byteRanges is initialised to an empty array on parse failure and
  isEndOfInput guards against null
- PF-48 FileService: suffix-range parsing (`Range: bytes=-N`) now
  returns exactly the last N bytes (was N+1, off by one)
- PF-52 FileService: multipart/byteranges responses are now well-formed
  -- Content-Range header (was the typo "ContentRange"), inter-part
  CRLF separators, and the closing --boundary-- delimiter

Resource lifetime:
- PF-41 FileService: write the body without flush, then writeAndFlush
  the LastHttpContent; the keep-alive close listener attaches to the
  trailer's future so the channel is not closed before the chunked body
  has drained
- PF-42 FileService: close the ChunkedInput (which owns the
  RandomAccessFile) when the channel was already closed before the
  write started, eliminating a per-request RAF leak
- PF-44 StreamChunkAggregator: 413 oversize rejection now deletes the
  partial spool file before clearing the reference; cleanupSpool() does
  not delete (the success path transfers ownership), so the rejection
  path needed an explicit unlink
- PF-45 PlayHandler: plugin rawInvocation paths now run cleanupSpooledBody
  in a finally; previously this only ran inside NettyInvocation, leaking
  one temp file per upload that hit the spool threshold whenever a plugin
  short-circuited the controller
- PF-46 PlayHandler: NettyInvocation now defers spool cleanup across
  suspend/resume via a `suspended` flag set in the suspend() override
  and reset at the start of each run(); the resumed invocation can read
  the body again
- PF-51 SslHttpServerContextFactory: PEM SSL trust manager now loads an
  empty in-memory keystore via `load(null, null)` before
  TrustManagerFactory.init(); the previous uninitialised keystore threw
  KeyStoreException on JDK 17+

Concurrency:
- PF-43 PlayHandler: staticPathsCache migrated to ConcurrentHashMap; the
  previous unsynchronized containsKey raced with the worker-thread put
  on the RenderStatic catch path. Synchronized blocks dropped
- PF-49 HttpServerPipelineFactory: classes cache migrated to
  ConcurrentHashMap; the previous shared HashMap.computeIfAbsent raced
  under concurrent initChannel calls
- PF-50 HttpServerPipelineFactory + SslHttpServerPipelineFactory: trim
  pipeline FQCNs before Class.forName; previously a leading space in
  play.netty.pipeline / play.ssl.netty.pipeline killed pipeline construction

Documentation:
- PF-53 configuration.textile: documents play.netty.maxContentLength
  semantic change (per-chunk cap -> hard 413 cap), the new
  play.netty.spoolThresholdBytes property, and the play.threads.virtual.*
  family (global toggle + per-subsystem overrides for invoker/jobs/mail)
- releasenotes-1.12.0.textile: promotes the "known limitations" and
  "out of scope" entries into "what's fixed" with one bullet per fixed
  ticket; updates verified-tests count to 299/299

Verified with `ant compile` and `ant unittest`.

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