patch hud dev proxy to call _hud_submit

[jdchawla29]

Fixes HUD-899

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Note

Medium Risk
Touches request dispatch (_call_tool) via monkey-patching in the Docker dev proxy path; regressions would impact dev-time tool invocation but not production runtime.

Overview
Fixes the Docker dev HTTP proxy so underscore-prefixed tools that are hidden from tool listings (notably _hud_submit) are still callable through hud dev --docker.

Adds a shared build_proxy() helper that wraps import_server() and patches MCPServer._call_tool to fall back to forwarding unknown tools directly to the backend tool manager; updates run_docker_dev_server to use this helper. Adds an async end-to-end test that spins up an HTTP Environment, builds the proxy, and verifies _hud_submit works despite not appearing in get_tools().

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