Add docstrings to all type stubs in python/natsrpy

[Copilot]

Adds comprehensive docstrings to all .pyi type stubs across the python/natsrpy/_natsrpy_rs/ package.

Changes

• __init__.pyi — Docstrings for Nats, IteratorSubscription, CallbackSubscription and all public methods
• exceptions.pyi — Docstrings for NatsrpyBaseError, NatsrpySessionError, NatsrpyPublishError
• js/__init__.pyi — Docstrings for Publication, JetStream, JetStreamMessage (class, all properties, all ack methods)
• js/stream.pyi — Docstrings for all enums (StorageType, DiscardPolicy, etc.), config/data classes (StreamConfig, StreamInfo, etc.), and Stream
• js/kv.pyi — Docstrings for KVStatus, KVOperation, KVEntry, iterators, KVConfig, and all KeyValue methods
• js/object_store.pyi — Docstrings for ObjectStoreConfig, ObjectInfo, ObjectLink, ObjectStore and all methods
• js/managers.pyi — Docstrings for StreamsManager, KVManager, ConsumersManager, ObjectStoreManager
• js/consumers.pyi — Docstrings for DeliverPolicy, AckPolicy, ReplayPolicy, PriorityPolicy, both consumer configs, MessagesIterator, PushConsumer, PullConsumer

Fixes to existing docstrings

• Fixed typos in JetStreamMessage.progress(): "Singnals" → "Signals", "mesasge" → "message"
• Fixed incorrect param name in JetStreamMessage.nack(): :param duration: → :param delay:
• Normalized docstring style to PEP 257 (no leading blank line, consistent punctuation)

Convention

Class docstrings use Attributes: sections for data/config classes. Method docstrings use Sphinx-style :param: / :return: notation, matching the pre-existing style in Stream.direct_get and JetStreamMessage.ack.