refactor(csharp): cleanup tcp connection after vsr implementation

[lukaszzborek]

Follow-up cleanup of the .NET SDK TCP transport after the VSR support landed

[codecov]

Codecov Report

❌ Patch coverage is 66.82135% with 143 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.93%. Comparing base (fb9307e) to head (aae1d4b).

Files with missing lines	Patch %	Lines
...SDK/IggyClient/Implementations/TcpMessageStream.cs	57.01%	40 Missing and 9 partials ⚠️
foreign/csharp/Iggy_SDK/Vsr/VsrConnection.cs	72.77%	40 Missing and 9 partials ⚠️
...IggyClient/Implementations/TcpMessageStream.Vsr.cs	53.62%	24 Missing and 8 partials ⚠️
foreign/csharp/Iggy_SDK/Consumers/IggyConsumer.cs	85.10%	2 Missing and 5 partials ⚠️
foreign/csharp/Iggy_SDK/Utils/ArrayPoolHelper.cs	75.00%	2 Missing and 1 partial ⚠️
...n/csharp/Iggy_SDK/Consumers/IggyConsumer.Rented.cs	0.00%	1 Missing and 1 partial ⚠️
foreign/csharp/Iggy_SDK/Mappers/BinaryMapper.cs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3858      +/-   ##
============================================
- Coverage     82.84%   81.93%   -0.92%     
  Complexity     1299     1299              
============================================
  Files          1199     1200       +1     
  Lines        161885   161835      -50     
  Branches     131360   131473     +113     
============================================
- Hits         134120   132595    -1525     
- Misses        24225    25644    +1419     
- Partials       3540     3596      +56     

Components	Coverage Δ
Rust Core	83.36% <ø> (ø)
Java SDK	66.06% <ø> (ø)
C# SDK	56.94% <66.82%> (-19.03%)	⬇️
Python SDK	89.98% <ø> (ø)
PHP SDK	84.26% <ø> (ø)
Node SDK	96.21% <ø> (ø)
Go SDK	68.53% <ø> (ø)

Files with missing lines	Coverage Δ
...n/csharp/Iggy_SDK/Utils/TcpMessageStreamHelpers.cs	91.42% <ø> (+6.64%)	⬆️
foreign/csharp/Iggy_SDK/Vsr/ConsensusSession.cs	98.98% <100.00%> (-1.02%)	⬇️
foreign/csharp/Iggy_SDK/Mappers/BinaryMapper.cs	82.10% <0.00%> (-11.39%)	⬇️
...n/csharp/Iggy_SDK/Consumers/IggyConsumer.Rented.cs	60.86% <0.00%> (-12.82%)	⬇️
foreign/csharp/Iggy_SDK/Utils/ArrayPoolHelper.cs	75.00% <75.00%> (ø)
foreign/csharp/Iggy_SDK/Consumers/IggyConsumer.cs	50.00% <85.10%> (-20.92%)	⬇️
...IggyClient/Implementations/TcpMessageStream.Vsr.cs	59.50% <53.62%> (-15.94%)	⬇️
...SDK/IggyClient/Implementations/TcpMessageStream.cs	51.10% <57.01%> (-32.06%)	⬇️
foreign/csharp/Iggy_SDK/Vsr/VsrConnection.cs	72.77% <72.77%> (ø)

... and 56 files with indirect coverage changes

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[lukaszzborek]

If possible, merge #3836 first. Then I will remove things with namespace which I refactoring 😅

[hubcio]

solid direction overall - classic framing gone, the VsrConnection extraction, typed namespaces and the epoch rejoin are real improvements. blocking items are the probe losing its reconnect, the never-nulled _connection, the fail-open namespace and the edge-based Disconnected clear; the rest is small.

one thing outside the diff: SetConnectionStateAsync (TcpMessageStream.cs:1153) is a non-atomic check-then-set with the publish after the write, reachable from callers holding different locks - concurrent transitions can publish duplicates or a PreviousState that never actually preceded CurrentState. it predates this PR, and fixing it properly means moving the publish behind an ordered queue (holding a lock across the publish is not an option - the handler chain runs synchronously into socket I/O when the semaphores are uncontended, so a sync write fault re-enters the same lock). follow-up material, but it is the substrate under the Disconnected-clear race flagged inline.