Feature: Use document extractors for grep and centralize file text extraction

[pfurovYnP]

(Codex)

#113

Motivation

• Ensure the same document text extraction logic used by read_file is also applied when searching files with grep_search so searchable content from PDFs/Office files is included.
• Reduce duplication by centralizing the extraction logic into helper functions.
• Improve error handling for binary/unsupported files in the grep flow to avoid reading raw bytes as text.

Description

• Introduced _extract_text_with_supported_document_extractors(file_path, mime) to encapsulate lookup and invocation of EXTRACTORS from open_terminal.utils.documents and return extracted text or None.
• Added _read_file_as_text_representation_for_grep(file_path) which mirrors read_file behavior: attempt UTF-8 read first, fall back to the document extractors, and raise UnicodeDecodeError for unsupported binary files.
• Refactored read_file to call the new extractor helper and simplified the previous inline extractor loop.
• Updated grep_search to use _read_file_as_text_representation_for_grep so document-extracted text is searched line-by-line, preserving existing match and truncation behaviour.

Testing

• Ran the automated test suite with pytest, and all tests completed successfully.
• Exercised read_file and grep_search behavior manually against text files and PDF/Office files to verify extracted text is returned and searchable as expected.
• Verified that binary files with allowed MIME prefixes are still returned as raw and unsupported binaries are rejected during search.