S24.09: StreamSender bad-setup contract — reject NULL Resolver / Stream / Address

[DavidCozens]

Parent epic: #254

Motivation

SolidSyslogUdpSender_Create validates its config and rejects NULL
Resolver / Datagram / Address / Endpoint with the bad-setup
contract from S12.06 — SolidSyslog_Error(ERR, ...) + nil-object
fallback (SolidSyslogNullSender).

SolidSyslogStreamSender_Create has no equivalent. It happily accepts
a config with NULL Resolver, NULL Stream, or NULL Address, then crashes
on the first SolidSyslogSender_Send when it dereferences the missing
collaborator. CodeRabbit flagged the new config->Address NULL path
on PR #422; deferred from S24.07 because adding only Address
validation without the other three would be inconsistent — fixing the
whole bad-setup contract together is its own atom.

This story brings StreamSender to the same bad-setup posture as
UdpSender.

Current state (audit 2026-05-25, main @ 4b3a361)

• Core/Source/SolidSyslogStreamSenderStatic.c::SolidSyslogStreamSender_Create
  has no IsValidConfig helper and no NULL-checks on config, Resolver,
  Stream, or Address. The only failure path it emits is
  STREAMSENDER_ERROR_POOL_EXHAUSTED.
• Core/Interface/SolidSyslogStreamSenderErrors.h enum lists only
  POOL_EXHAUSTED, UNKNOWN_DESTROY, MAX.
• Core/Source/SolidSyslogStreamSenderMessages.c carries only those two
  message strings.
• Tests/SolidSyslogStreamSenderTest.cpp has no SolidSyslogStreamSenderBadSetup
  TEST_GROUP — grep for BadSetup / NULL_RESOLVER returns nothing.

No prior work landed on this story; all four acceptance criteria are
outstanding.

Acceptance criteria

• SolidSyslogStreamSender_Create rejects config == NULL,
  config->Resolver == NULL, config->Stream == NULL, and
  config->Address == NULL with distinct
  STREAMSENDER_ERROR_NULL_{CONFIG,RESOLVER,STREAM,ADDRESS} codes
  (naming matches the UDPSENDER_ERROR_NULL_* convention).
• On bad config, _Create returns SolidSyslogNullSender_Get() —
  pool slot is not consumed. Matches SolidSyslogUdpSender_Create's
  IsValidConfig/early-return shape
  (Core/Source/SolidSyslogUdpSenderStatic.c:48-76).
• Existing tests pass; new TDD-driven tests cover each of the four
  NULL paths (mirroring the SolidSyslogUdpSenderBadSetup tests at
  Tests/SolidSyslogUdpSenderTest.cpp:763-823).
• CLAUDE.md SolidSyslogStreamSender.h row updated to note the
  bad-setup contract (currently says "Pool exhaustion resolves to
  the shared SolidSyslogNullSender"; extend with the bad-config
  fallback as the SolidSyslogUdpSender.h row already does).
• No behaviour change for existing valid wirings — only adds the
  NULL-rejection paths.

References

• S12.06 — established the bad-setup contract.
• S24.07 — added config->Address to StreamSenderConfig; deferred the
  matching bad-setup validation.
• PR feat!: S24.07 SolidSyslogAddress as pool-allocated handle #422 — CodeRabbit raised the missing validation.