Fix zlib-compressed ASS dialogue forwarding from Matroska

[rubinaboobin3-cell]

This fixes ASS/SSA subtitle rendering for Matroska files whose ASS dialogue payloads are zlib-compressed.

The previous overlay path forwarded dialogue bytes using:

data = sample.data
offset = lineIndex
length = sample.limit() - lineIndex

That works for plain text ASS payloads, but fails for zlib-compressed payloads. Compressed data may contain embedded NUL bytes, and Media3's subtitle sample limit can represent a truncated text-like slice instead of the full compressed payload. Passing only sample.limit() - lineIndex can therefore send an incomplete compressed stream to libass.

Fix

AssTrackOutput now:

• detects zlib-looking dialogue payloads at the ASS dialogue offset,
• copies compressed payloads from the full raw backing buffer,
• inflates them before forwarding to AssHandler.readTrackDialogue,
• keeps the previous bounded sample.limit() behavior for normal uncompressed ASS payloads,
• falls back to the original bytes if inflation fails.

Why

Without this, affected fansub MKVs can show symptoms such as:

• missing dialogue lines,
• broken signs/typesetting,
• raw-looking ASS override fragments appearing on screen,
• intermittent subtitle lines because compressed events are truncated before libass receives them.

The important detail is that zlib inflation must use the full raw sample backing buffer / actual block payload, not the truncated subtitleSample.limit() slice.

Scope

This change is limited to the Media3 Matroska ASS forwarding path in:

lib_ass_media/src/main/java/io/github/peerless2012/ass/media/text/AssTrackOutput.kt

It does not change renderer selection, overlay behavior, font handling, or normal uncompressed ASS forwarding.

Testing

This was validated downstream in an app using libass-android with a Matroska sample containing zlib-compressed ASS dialogue packets. Before the fix, dialogue and signs were missing or broken. After inflating from the full raw sample buffer, dialogue, signs, and effects rendered correctly.