feat(rdws): add supervisor-update methods and fix GetLogs

[kkennedy-bs]

Adds the rDWS methods needed to drive and observe a supervisor update on a player, and fixes GetLogs so it can succeed at all.

New RDWSService methods (each follows the existing rdws.go shape: validate, ensure auth + network context, build the destination-scoped URL, unwrap data.result):

• TriggerUpdateSync POST /update/sync
• GetStoredSupervisors GET /system/supervisors
• DeleteSupervisors POST /system/supervisors/delete (builds/clear are
  mutually exclusive; rejected client-side too)
• GetCrashDumpFiles GET /logs/crash-dumps
• GetSystemInfo GET /system -- EXPERIMENTAL: an Internal-tier,
  undocumented route, reachable only because the rDWS
  passthrough originates from localhost. It is the only
  source for the running supervisor version, so it is
  provided with a caveat rather than left to every
  caller to hand-roll.

Fixes:

• GetLogs treated a string result as a device error, but GET /logs returns dmesg AS a string, so the method could never succeed on a healthy player. A string result is now the success case (RDWSLogs.Text); a structured list is still accepted. Genuine device errors arrive as non-2xx and are handled before this parse, so nothing is lost.

New public type aliases in gopurple.go so external consumers can use the new methods without importing internal/types. RDWSLogs gains a Text field additively; no existing field or signature changes, so this is a safe drop-in.

Tests: parseLogsResult and parseCrashDumpList table tests (the log fix fails against the prior logic, confirming it tests the fix), plus interface conformance, empty-serial/no-auth guards, request-shape validation, and response-parsing for the system-info and stored-supervisor shapes.