fix(ci): require native boundary responses after bounded reset retries

[2217173240]

Main’s Windows AMD64 native check failed while reading the HTTP response to a hostile loopback POST (ConnectionResetError: WinError 10054, run 38034106161). Setup GET had passed; the log does not establish the reset’s cause.

The smoke helper now retries only connection-reset exceptions before an HTTP response, at most three attempts. Each Host/Origin case must still independently receive HTTP 403. Persistent resets, accepted requests, wrong HTTP status, and unrelated transport/protocol errors fail; response handles are closed. Production launcher behavior is unchanged.

Validation: all 10 native helper tests passed, including six new regression methods and an actual loopback server that disconnects before returning 403 for both headers; a freshly built macOS ARM64 native-channel executable passed setup, sanitized status, both boundaries, and graceful stop. Independent read-only 6.1 Sol review found no actionable issue. Existing test_native*.py CI discovery includes the regression file.

Exception handling follows the Python urllib error model: HTTPError is handled before its URLError parent; only an actual reset reason is retried. Cloud native installation checks remain required before merge.