[FIX] Minor fixes + Stylistic enhancements for TQDM and Multiprocessing

[bhavnicksm]

This pull request includes several changes to the chonkie package, focusing on updating progress bar descriptions, improving error messages, and adding docstrings for better code clarity. The most important changes include modifications to progress bar descriptions in multiple files, updates to error messages in semantic.py, and the addition of docstrings in auto.py and base.py.

Progress bar description updates:

• src/chonkie/chunker/base.py: Updated progress bar descriptions in _process_batch_sequential and _process_batch_multiprocessing methods to use "doc" instead of "texts" and changed the bar format and ASCII style. [1] [2]
• src/chonkie/chunker/token.py: Updated progress bar description in chunk_batch method to use "batch" instead of "batches" and changed the bar format and ASCII style.

Error message improvements:

• src/chonkie/chunker/semantic.py: Improved error messages in the __init__ method to provide more specific information about invalid embedding models.
• src/chonkie/embeddings/auto.py: Changed the error handling in get_embeddings method to raise a ValueError instead of issuing a warning when an embedding class fails to load.

Code clarity enhancements:

• src/chonkie/embeddings/auto.py: Added a docstring to describe the AutoEmbeddings class.
• src/chonkie/embeddings/base.py: Added a docstring to describe the base class for all embeddings implementations.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/chonkie/embeddings/auto.py	0.00%	1 Missing ⚠️

Flag	Coverage Δ
python-3.10	67.37% <66.66%> (+0.02%)	⬆️
python-3.11	67.37% <66.66%> (+0.02%)	⬆️
python-3.12	67.37% <66.66%> (+0.02%)	⬆️
python-3.13	67.37% <66.66%> (+0.02%)	⬆️
python-3.9	67.29% <66.66%> (+0.02%)	⬆️

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Files with missing lines	Coverage Δ
src/chonkie/chunker/base.py	58.55% <100.00%> (ø)
src/chonkie/chunker/semantic.py	59.11% <ø> (ø)
src/chonkie/chunker/token.py	70.73% <ø> (ø)
src/chonkie/embeddings/base.py	59.45% <100.00%> (+1.12%)	⬆️
src/chonkie/embeddings/auto.py	62.96% <0.00%> (ø)