Fix command-tracing context bleed across HTTP requests

Command tracing occasionally publishes a command under an unrelated request (and/or more than once): CommandTracingFilter read the in-flight command from a thread-bound ServerRequestContext that can be stale on a reused reactive worker, so a bystander request re-published a prior request's command — wrong http_method, duplicate command_log rows.

Fix: resolve the command from the Reactor subscription context (ServerRequestContext.currentRequest(ContextView)) instead of the thread-bound lookup.

Details: plans/2026-06-17_11__conta-command-tracing-context-bleed.md (diagnosis), plans/2026-06-18_11__conta-command-tracing-fix-mechanism.md (fix mechanism — best current knowledge).