panic: byte index is not a char boundary in wagl ingest transcripts

[GoZumie]

Bug

wagl ingest transcripts panics when transcript content contains multi-byte UTF-8 characters (e.g. curly quotes " ").

Error

thread 'main' panicked at 'byte index 2000 is not a char boundary'

Root Cause

The ingest logic is slicing strings at a fixed byte offset (e.g. 2000) rather than a character boundary. In Rust, &str[n..] requires n to fall on a valid UTF-8 char boundary. Curly quotes and other non-ASCII characters are 2-3 bytes in UTF-8, so a fixed byte slice can land mid-character.

Fix

Use char_indices() or a manual char-boundary walk to truncate safely:

fn safe_truncate(s: &str, max_bytes: usize) -> &str {
    if s.len() <= max_bytes {
        return s;
    }
    let mut boundary = max_bytes;
    while !s.is_char_boundary(boundary) {
        boundary -= 1;
    }
    &s[..boundary]
}

Reproduction

Run wagl ingest transcripts on any transcript containing curly quotes, em-dashes, or other multi-byte UTF-8 characters near a chunk boundary.