fix: SHIP handshake conformance (CMI/PROT/TERM abort behavior)

[andig]

Closes #98. Contributes to #95 (SHIP TestSpecification V1.0.0 compliance).

Fixes six non-conformances against the SHIP High-Level Test Specification, all in the handshake / connection-lifecycle abort paths. #98 covers PROT_003/004; this PR also resolves CMI_001, PROT_005/006 and TERM_001 in the same area.

TC	Before	After
CMI_001	server dropped an invalid CMI message with no reply	sends CMI {0,0} reject before closing
PROT_003	server proto-handshake wait-timer expiry sent no frame	sends protocolHandshakeError error=1 (timeout)
PROT_004	client wait-timer expiry sent error=2	sends error=1 (timeout)
PROT_005	server unexpected/malformed proposal sent no frame	sends error=2 (unexpected message)
PROT_006	client valid-but-non-select sent error=3	sends error=2 (unexpected message); malformed select stays error=3 (selection mismatch)
TERM_001	announced close carried raw caller string (e.g. "User close") as reason	maps free-form reasons to a valid ConnectionCloseReasonType (unspecific)

How

• Timeouts are now handled in the handleState dispatch for the server/client protocol-handshake states before the message handler runs, so a nil-message timeout is not misclassified as an unexpected message.
• The proposal/choice handlers use abortProtocolHandshake (which emits the error frame) instead of endHandshakeWithError (which does not) for message-rejection paths; genuine send errors still use endHandshakeWithError.
• The client choice handler distinguishes "not a select at all" (unexpected message, error=2) from "a select with bad version/format" (selection mismatch, error=3).
• validCloseReason sanitizes the announced close reason.

Tests

New/updated conformance tests assert the exact SHIP error codes on the sent frame (Test_ListenProposal_Timeout, Test_ListenProposal_Failure, Test_ListenChoice_Timeout, Test_ListenChoice_UnexpectedMessage, Test_ListenChoice_SelectionMismatch, Test_ServerWait_Invalid*, TestValidCloseReason). Every test is annotated with its TC id. Full module test suite passes.

🤖 Generated with Claude Code

[coveralls]

coverage: 92.88% (-0.1%) from 92.993% — andig:fix/ship-handshake-conformance into enbility:dev