#16327: fix(bluebubbles): enforce dmPolicy for DMs; block unknown senders when pairing/allowlist

When allowFrom was empty, isAllowedBlueBubblesSender always returned true, so pairing/allowlist were never applied. Now pass dmPolicy and return false for empty allowFrom when dmPolicy is "pairing" or "allowlist". Fixes #16108 <!-- greptile_comment --> <h3>Greptile Summary</h3> This PR aims to fix a bug where `isAllowedBlueBubblesSender` always returned `true` when `allowFrom` was empty, bypassing "pairing" and "allowlist" DM policies. The fix passes `dmPolicy` into the function and returns `false` for empty `allowFrom` when the policy requires restriction. - **Blocker: Unresolved merge conflict markers** in `extensions/bluebubbles/src/targets.ts` (lines 334-386) — the file contains `<<<<<<<`, `=======`, and `>>>>>>>` markers, making it uncompilable. The merge with `main` was not properly resolved. - The branch-side resolution duplicates all matching logic from the shared `isAllowedParsedChatSender` helper in `src/plugin-sdk/allow-from.ts`. A cleaner fix would add the `dmPolicy` guard *before* delegating to the shared helper, keeping the codebase DRY. - The call sites in `monitor-processing.ts` correctly pass the new `dmPolicy` parameter. - Test coverage is solid, covering pairing/allowlist blocking, backward compatibility, handle matching, and wildcard support. <h3>Confidence Score: 1/5</h3> - This PR cannot be merged — it contains unresolved git merge conflict markers that will cause a compilation failure. - Score of 1 reflects the presence of unresolved merge conflict markers in targets.ts (lines 334-386), which is a compile-breaking issue. The intended logic change is sound, but the file is not in a valid state. Additionally, the implementation duplicates shared SDK logic rather than composing with it. - extensions/bluebubbles/src/targets.ts — contains unresolved merge conflict markers that must be resolved before this PR can be merged. _{Last reviewed commit: 51c4a2b} <!-- greptile_other_comments_section --> <!-- /greptile_comment -->