fix(herdr): Improve AGY parser line wrapping and prompt marker matching

[linuxse-blue]

Description

This PR improves the Herdr provider adapter for Codex and AGY agents:

• Prompt Marker Matching: Uses rposition() instead of position() to find the latest prompt marker in TUI output.
• Line Filtering: Correctly preserves all prose response lines with leading spaces while skipping TUI status bars.
• Exact Line Break Preservation: Preserves original multi-line terminal line breaks for clean Telegram delivery.

Verification

• Verified turn response streaming and multi-line Telegram message parsing.