macOS crash: inverted Markdown link range in Zeron 0.2.112 #892

Zeron 0.2.112 crashes while preparing a Markdown link label for rendering. The link text is sliced with an inverted byte range (104..96), causing a Rust panic and aborting the application.

The crash occurred on October 13, 2026, at 17:17:51 -0300 (20:17:51 UTC), on macOS 27.0.1 (26A434), Apple M4 Pro / arm64. The main thread aborted with SIGABRT. The application log records:

2026-10-13T20:17:51.570630Z
panicked at crates/ui/src/markdown/render.rs:1319:47:
byte range starts at 104 but ends at 96

The installed 0.2.112 executable matches the report UUID: AB9F75E3-4925-390A-BC79-55886DEFD583. Binary inspection confirms ResponsiveText::prepaint in the call stack and a call to core::str::slice_error_fail at the failing caller.

The panic occurs while extracting a Markdown link label in render.rs:1319:

.map_or(&flat.text[range.clone()], |original| {
    &original.text[original.offsets.original(range.start)
        ..original.offsets.original(range.end)]
})

The immediate problem is an inverted text range (104..96), rather than a font run ending inside →. Related issue: #280 covers a font-run UTF-8 boundary panic. This report tracks a different immediate failure; a shared root cause has not been established.

The content or transformation that produced the inverted range is not yet identified, and no application reproduction has been confirmed. The external-reload fixture proposed for #280 has not been shown to reproduce this Markdown crash. Investigation so far was read-only; no fix or regression test was added.