[SunSi12138]

Fixes #575

Summary

• add an on-demand, bounded Client/connection support snapshot API in SharpLink.Client
• export schema-versioned redacted JSON with endpoint/connection truncation totals and a hard UTF-8 size cap
• use NativeAOT-safe System.Text.Json source generation for both pretty and compact export; no reflection-based JSON serialization or runtime enum converter generation
• reuse existing readiness, policy generations, connection/session owners, pending-request counts, stream counts, send-queue byte counters, and negotiated session state instead of introducing RPC-path history
• expose safe endpoint ordinals/transport categories and coarse failure classifications; never export raw endpoint addresses/attributes, metadata, payloads, exception messages/data, environment variables, command lines, credentials, private material, or callback targets
• keep capture weakly consistent and on-demand: capture owned state into bounded DTOs before JSON serialization, without holding connection/global locks across export
• document the support-snapshot workflow in doc/troubleshooting.md

Acceptance coverage

• empty/not-connected and ready connection snapshots
• static multi-endpoint totals/truncation and convergence while another endpoint is connecting
• fixed draining connection capture
• pending usage near configured capacity using the existing pending owner
• negotiated protocol/resource fields and safe compression/runtime configuration summary
• real fixed dial, TLS, and handshake failures plus auth/protocol safe-classification coverage
• endpoint/auth/metadata/URI-credential sentinel redaction in final JSON
• dynamic endpoint replacement raced with repeated capture
• Stop raced with repeated snapshot/JSON capture and post-stop repeated capture
• deterministic schema version, pretty/compact export, and hard JSON byte limit

Validation

Final head: 017cc8da5ddca63416016803aa939d2e17dbe7c4

• PR Fast: success
  • Release build
  • generated-assembly dependency guard
  • 1,669 Unit Tests
  • 264 Generator Tests
  • 60 Load Test Tests
  • deterministic managed-allocation gate
• PR Quick: success
  • Debug + Release build
  • 1,669 Unit Tests
  • Generator + Load Test Tests
  • 451 Integration Tests
  • NativeAOT transport/topology smoke
  • pack + NuGet package contract/smoke
  • demo, load, and chaos smoke
• CodeQL: success
• Extension fault containment: success
• Pending and codec validation: success
• format, project-reference boundary, and maintainability gates: success

The first PR Fast attempt on the final head hit one unrelated existing timed-unary emission test timeout; the same-head PR Quick Unit run and the PR Fast rerun both passed all 1,669 tests.

[SunSi12138]

整体方向和 redaction/有界 JSON 设计是合理的，exact-head CI 也已通过。当前有两个 cluster diagnostics 语义缺口值得在合并前处理：cluster 拓扑只从 ready connection 反推，导致 connecting/retiring/资源统计丢失；以及 last connection failure 目前没有接入 static/dynamic cluster 的真实失败路径。两点都直接影响 #575 的核心排障价值，见 inline。

[SunSi12138]

Final re-review: both substantive cluster-diagnostics findings are resolved on exact head 6c71d799f88399d1a3457bc7ecfccf039ffc0f44.

• Cluster topology is now captured from the static/dynamic runtime owners under their existing gates, so connecting, retiring/draining connections, real transport category, totals, and aggregate pending/active/stream/send-queue resources are retained without adding RPC hot-path history/state.
• Last connection failure is now published from real resolver and static/dynamic connection-establishment failure paths. Raw endpoint ids are not retained in the publication; static endpoint indices / dynamic per-state generations are mapped to snapshot-local endpoint-XXXX ordinals at capture time.
• Added review regressions cover static convergence/transport, dynamic retiring resources, real static/dynamic dial failures, and resolver failure/redaction.
• The reviewed branch is behind_by=0 against dev@fde86f91c327f2de1234cd70efbf9ea7b675c9e0. Exact-head PR Fast #1470, PR Quick #2755, CodeQL #3787, Extension fault containment chore(deps): bump github/codeql-action from 4.37.4 to 4.37.6 #97, and Pending and codec validation [generator][DX] Hide generated Proxy/Stub implementation types from IntelliSense #161 are all successful.

No new correctness/redaction/boundedness blocker was found. #645 has been squash-merged into dev as 9cfa3640af77b356b98f4110d99ad5ca3929b229. The earlier timed-unary CI recurrence remains tracked separately in #387 and is not attributed to this PR.