Respect chunk_size in default chunking strategies across reader classes

Reader classes now correctly propagate the chunk_size parameter to the default chunking strategy they apply when no explicit chunking configuration is provided. Previously, chunk_size set on a reader was silently ignored when falling back to the default chunker, producing chunks of unexpected size.

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Details:

Fixes chunk_size being ignored in default chunking strategies used by reader classes
Ensures consistent chunk sizing across both explicit and default chunking configurations
No changes required; the fix applies automatically to all reader classes