Previously, if serde_json::from_str failed on a streamed line, the
line was silently discarded and the caller had no indication that data
was lost. Now parse errors are yielded as OllamaError::ResponseParseError
so consumers can detect and handle unexpected API responses.
Empty lines from LinesCodec are skipped to avoid spurious parse errors
on blank input between chunks.
Store a shared reqwest::Client on OllamaClient instead of creating
a new one per request. Previously, version(), tags(), and ps() each
used reqwest::get() which allocates a one-shot client, and
stream_response() called reqwest::Client::new() on every invocation.
Since reqwest::Client manages an internal connection pool, reusing it
enables TCP and TLS connection reuse across calls. Cloning the client
is cheap as it is Arc-backed internally.
