Refactor only.

• Rename allowTagsWhenOff -> allowExplicitReplyTagsWhenOff.
• Fail closed for unknown channels when replyToMode=off (keep webchat allowed).
• Consolidate reply threading/tag parsing into a single helper.

Tests: pnpm check, pnpm test.

Greptile Overview

Greptile Summary

Clean refactoring of the reply threading/tag system with one deliberate behavioral tightening:

• Renames allowTagsWhenOff to allowExplicitReplyTagsWhenOff across the type, dock, plugin, and filter layers for clarity.
• Consolidates implicit reply threading, tag parsing, and replyToCurrent resolution into a single resolveReplyThreadingForPayload helper, reducing duplication in reply-payloads.ts.
• Broadens the "explicit" check in createReplyToModeFilter to include replyToCurrent (not just replyToTag), which compensates for the removed replyToTag ?? true default.
• Behavioral change: unknown channels now fail closed when replyToMode=off (previously defaulted to allowing tags). Internal webchat channel is explicitly exempted. This is a security improvement.
• Tests updated accordingly; existing integration tests confirm no regression.

Confidence Score: 5/5

• This PR is safe to merge — it's a well-scoped refactor with one intentional security tightening, backed by passing tests.
• The changes are primarily mechanical renames plus a consolidation of duplicated logic into a single helper. The one behavioral change (fail-closed for unknown channels) is a deliberate security improvement. All existing tests pass, the old property name is fully removed, and the refactored code paths are logically equivalent to the originals.
• No files require special attention.

_{Last reviewed commit: e8ebc8e}