fix: correct path references in batch_convert_html.sh

[handsomesix]

Summary

Fix the make doc command execution failure. Adjust the directory switching and script reference logic in batch_convert_html.sh to ensure the documentation conversion script runs from the correct path.

Root Cause

batch_convert_html.sh has multiple path handling issues:

1. Initial directory switching uses SCRIPT_DIR/../, which enters the tools/ directory instead of the project root.
2. Converter script references use ./converters/, but that path doesn't exist in the current working directory.
3. Input directory existence check is performed after entering the scripts/ directory, causing path judgment based on the wrong working directory.

These issues collectively prevent make doc from correctly locating the conversion scripts and documentation directories.

Changes

• Adjusted initial directory switching from SCRIPT_DIR/../ to SCRIPT_DIR/../../ to ensure entering the project root.
• Changed converter script reference path from ./converters/ to ../tools/converters/.
• Moved directory existence check to before entering the scripts/ directory to avoid path judgment issues caused by working directory changes.

Tests

• Execute make doc to verify the script workflow.
• Confirm that documentation conversion script paths can be correctly resolved.
• Confirm that directory checking logic works correctly.
• Current remaining errors are due to missing PyYAML dependency, which is unrelated to this path fix.

Risk

Low.

Only modified the path handling logic in the documentation build script, no runtime code or model functionality changes.

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