feat(go): implement TCP/TLS connection in Go SDK

[saie-ch]

Which issue does this PR close?

This unblocks issue #2807 so TCP/TLS integration tests and examples can now be written for the Go
SDK.

Rationale

The Go SDK had TLS configuration fields (tlsEnabled, tlsDomain, tlsCAFile, tlsValidateCertificate)
and TLS error types generated, but the handshake was stubbed out at line 329 with return
errors.New("TLS connection is not implemented yet"). This blocked writing integration tests and
examples for TCP/TLS connections.

What changed?

Before: Line 329 returned a stub error preventing any TLS connections.

After: Full TLS implementation with:

• Added 4 TLS configuration option functions: WithTLS(), ### WithTLSDomain(), WithTLSCAFile(),
  WithTLSValidateCertificate()
• Implemented createTLSConfig() helper method that:
  • Configures certificate validation (InsecureSkipVerify)
  • Extracts server name from address for SNI (if tlsDomain not provided)
  • Loads custom CA certificates from file
  • Returns appropriate TLS error types (ErrInvalidTlsDomain, ErrInvalidTlsCertificatePath,
    ErrInvalidTlsCertificate)
• Replaced stub with actual TLS handshake using crypto/tls (lines 360-373):
  • Creates TLS config
  • Wraps TCP connection with tls.Client()
  • Performs TLS handshake with proper error handling

Implementation follows the same patterns as Rust (tcp_tls_connection_stream.rs), Java
(InternalTcpClient.java), C# (TcpMessageStream.cs), and Node.js (client.connection.ts) SDKs.

AI Usage

Claude Sonnet 4.5

• Guided by existing Rust, Java, Node.js, and C# TLS implementations
• Followed Go SDK patterns and used existing error types
• All pre-merge checks passed locally

[codecov]

Codecov Report

❌ Patch coverage is 0% with 42 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.55%. Comparing base (3432714) to head (aae02e2).
⚠️ Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
foreign/go/client/tcp/tcp_core.go	0.00%	42 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (50.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2834      +/-   ##
============================================
- Coverage     67.58%   67.55%   -0.04%     
  Complexity      708      708              
============================================
  Files          1027     1027              
  Lines         83147    83188      +41     
  Branches      60004    60004              
============================================
  Hits          56195    56195              
- Misses        24612    24653      +41     
  Partials       2340     2340              

Flag	Coverage Δ
go	6.77% <0.00%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
foreign/go/client/tcp/tcp_core.go	0.00% <0.00%> (ø)

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[hubcio]

where are tests?