Fix scanner findings: dead code and secrets false positive

Remove the unused sendRejection helper left behind by the Go transport
deduplication (staticcheck U1000, failing the Static Analysis
workflow). Truncate a full 40-hex commit SHA in SOW-0015 to its short
form: written next to the word SonarCloud it pattern-matched the
Semgrep detected-sonarqube-docs-api-key secrets rule, failing every
Codacy Local Analysis run since June 8 and raising two false-positive
code scanning alerts.

Author: ktsaou

.agents/sow/current/SOW-0015-20260605-codacy-scope-and-maintainability.md

@@ -908,7 +908,8 @@ Validation for this increment:
 
 Fresh Netdata PR #22649 SonarCloud evidence after vendoring plugin-ipc commit `f5eca1e`:
 
-- SonarCloud analyzed Netdata PR head `08fcd6594fec0f5f3fa323946e35cf7354f0fe0f`.
+- SonarCloud analyzed Netdata PR head `08fcd6594fec` (short SHA; the full hash
+  trips secret scanners when written next to the word SonarCloud).
 - SonarCloud new-code duplication improved from 1024 lines / 5.903378300472731% to:
   - new duplicated lines: 666.
   - new duplicated blocks: 33.

src/go/pkg/netipc/transport/posix/uds_handshake.go

@@ -138,10 +138,6 @@ func serverHandshake(fd int, config *ServerConfig, sessionID uint64) (*Session,
 	}, nil
 }
 
-func sendRejection(fd int, status uint16) {
-	_ = sendHelloAck(fd, status, protocol.HelloAck{LayoutVersion: 1})
-}
-
 func sendHelloAck(fd int, status uint16, ack protocol.HelloAck) error {
 	pkt := framing.BuildHelloAckPacket(status, ack)