Greptile Summary

Added thread-aware channel-specific model overrides via channels.modelByChannel configuration. The feature allows pinning specific channels/groups to models while respecting the priority hierarchy: heartbeat model > session override (/model) > channel override > defaults. Thread awareness enables fallback from thread IDs to parent channel IDs when direct matches aren't found, with support for Telegram topic suffixes (:topic:99) and Discord/Slack thread patterns (:thread:456).

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The implementation is well-structured with comprehensive tests covering parent group ID fallback, topic-specific overrides, and thread-aware matching. The logic correctly prioritizes overrides (heartbeat > session > channel > defaults) and integrates cleanly with existing model selection code. Documentation is thorough and the feature is non-breaking.
• No files require special attention

_{Last reviewed commit: 68e7d1c}