docs: correct drifted and fabricated APIs in chapters 13/17/35/51

An audit of doc code blocks against the real headers found APIs that do
not exist in the codebase, presented as authoritative walkthroughs:

- ch35 (dispatch): an entirely fabricated callback architecture —
  HostCommandRegistry::set_emit_ceid_handler, CommandOutcome, emit_ceids.
  Rewritten to the real Spec/Result/dispatch + the new set_handler hook.
- ch13 (E30): wrong store names — EventStore/ReportStore -> EventReportSubscriptions,
  SvidStore -> StatusVariableStore, AlarmStore/AlarmDispatcher -> AlarmRegistry,
  ClockStore -> Clock, TerminalServiceStore -> (no store), in both the
  capability tables and the worked S2F33 example.
- ch17 (E116): EptStore/seconds/bucket_ -> EptStateMachine/milliseconds/buckets_.
- ch51 (extending): stale host-command handler -> the real set_handler signature.

Verified clean by grep: no fabricated symbols remain in docs/.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/17_e116_e120_e39_objects.md

@@ -61,9 +61,9 @@ tracks: **how long was the equipment in each state**.
 The store accumulates time-buckets:
 
 ```cpp
-class EptStore {
+class EptStateMachine {
   // For each EptState, accumulated wall-clock duration.
-  std::array<std::chrono::seconds, 6> bucket_;
+  std::array<std::chrono::milliseconds, 6> buckets_{};
 
   // Current state + when it was entered (so the dwell so far is
   // counted as part of the current bucket on read).