fix: Repair corrupted session files instead of chasing parentUuid chains

Replace the BFS chain-following logic for session resolution with
in-place repair of corrupted JSONL session files. Fixes three known
corruption patterns: snapshot messageId collisions, broken parentUuid
references, and disconnected compaction roots.

Ported from the Python repair logic shared in claude-code#24304
(anthropics/claude-code#24304) as a
workaround for Claude Code's session file corruption bugs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 2witstudios