feat(http): implement short polling for reverse shell and create portal

[hulto]

This PR introduces short polling over HTTP/1.1 to implement Reverse Shell and Create Portal capabilities for agents connecting over HTTP rather than direct gRPC or DNS.

Changes include:

• tavern/internal/redirectors/http1/grpc_stream.go: Added ReverseShell and CreatePortal stream config definitions.
• tavern/internal/redirectors/http1/redirector.go: Hooked up handlers for /c2.C2/ReverseShell and /c2.C2/CreatePortal.
• tavern/internal/redirectors/http1/handlers.go: Implemented handleShortPollStreaming which receives a request, sends any embedded gRPC payloads to the backend stream, reads waiting items, and flushes them as a response to the same POST cycle.
• implants/lib/transport/src/http.rs: Implemented handle_short_poll_streaming and connected it to ReverseShell and CreatePortal interfaces. Agents loop repeatedly posting data buffers and waiting for server instruction.

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PR created automatically by Jules for task 7032004942279343568 started by @hulto

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[github-actions]

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
2816    ±0	2816    ±0	0    ±0	0    ±0	0    ±0	0    ±0	1ms    ±0

Previous Results

Build 🏗️	Result 🧪	Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
#1708	✅	2816	2816	0	0	0	0	39.0s

Insights

Average Tests per Run	Total Flaky Tests	Total Failed	Slowest Test (p95)
2816	0	0	5.6s

Slowest Tests

Test 📝	Results 📊	Duration (avg) ⏱️	Duration (p95) ⏱️
TestDockerExecutor_Build_ContextCancellation	1	5.6s	5.6s
eldritch-libsys: std::dll_inject_impl::tests::test_dll_inject_simple	1	5.2s	5.2s
TestInteractiveShell	1	5.1s	5.1s
TestOtherStreamOutput	1	5.0s	5.0s
imix::bin/imix: install::tests::test_install_execution	3	1.8s	5.0s
imix::bin/imix: install::tests::test_install_execution	3	1.8s	5.0s
imix::bin/imix: install::tests::test_install_execution	3	1.8s	5.0s
TestDockerExecutor_Build_SimpleEcho	1	3.7s	3.7s
imix::bin/imix: tests::task_tests::test_task_streaming_output	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_streaming_output	3	3.0s	3.0s

_{🎉 No failed tests in this run. | 🍂 No flaky tests in this run.}

Github Test Reporter by CTRF 💚

🔄 This comment has been updated

[hulto]

@jules first pass