…ance class

…assessment doc

- PathObjectSubscriptionOptions: validate depth fail-fast per RTPO19c1a,
  throwing AblyException with ErrorInfo(400, 40003) when depth <= 0.
  Depth is now a primitive int; the "no depth / infinite depth" state is
  expressed via a new no-arg constructor (mirrors ably-js `{}` options),
  so no null handling is needed
- LiveMapValue: defensively copy binary payloads on creation and access,
  making the RTLMV3d immutability guarantee real for byte[] values
- ObjectData#getBytes: document that the returned array is the underlying
  message payload and must be treated as read-only
- JsonObjectPathObject/JsonArrayPathObject: reword "primitive resolution"
  javadoc for clarity
- LiveMapPathObject#at: fix javadoc equivalence example to compile
  (get() returns base PathObject, so chain via asLiveMap())

…al-public-api

[LiveObjects] Implement path-based LiveObjects public API

- PathObject path parsing: exact port of the ably-js escape algorithm
  (backslash before a non-dot is kept literally, so an escaped backslash
  no longer suppresses the dot split; trailing backslash kept as-is)
- PathObjectSubscriptionRegister: deliver one event per full path to the
  updated object, so an object reachable via several covered paths
  notifies subscribers once per path (mirrors
  liveobject.ts#_notifyPathSubscriptions)
- size()/keys()/entries() on map path objects and size() on map
  instances now exclude entries with unresolvable (dangling/tombstoned)
  object references, per RTLM10d/RTLM14
- Added parity tests for escaped-backslash parsing, multi-path event
  delivery, and unresolvable-reference filtering