Standardize on top-level triggerer property (#361)

* Standardize on top-level `triggerer` property

- Rename `triggeringUser` → `triggerer` as the single top-level payload property
- Remove redundant `triggerer` from `FixReviewEvent`, add `approvedOnly` boolean
- Auto-apply `approved_by` filtering in `get_review_comments` when `approvedOnly` is set
- Auto-assign created PRs to the triggerer
- Simplify `AddressReviews` mode prompt
- Accept both `triggerer` and `triggeringUser` in schema for backward compat

* Address review feedback: simplify approved_only, remove addAssignees, drop approved_by param

* Fix formatting in `action/mcp/pr.ts`

* re-add triggeringUser backward-compat fallback in payload schema

* auto-assign created PRs to the triggerer

* Revert "auto-assign created PRs to the triggerer"

This reverts commit c088c425fea33793eb299a001ffd253798d2c674.

* Revert "re-add triggeringUser backward-compat fallback in payload schema"

This reverts commit ae5b3cb3f1377cd4a634b2d48962c785c31013f3.

* backend compat

* tweak prompt to ensure compat

* Address review feedback

* chore: remove triggeringUser fallback

---------

Co-authored-by: pullfrog[bot] <226033991+pullfrog[bot]@users.noreply.github.com>
Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>
Co-authored-by: Colin McDonnell <colinmcd94@gmail.com>

external.ts

@@ -229,8 +229,8 @@ interface FixReviewEvent extends BasePayloadEvent {
   issue_number: number;
   is_pr: true;
   review_id: number;
-  /** username of the person who triggered this action - use with get_review_comments approved_by */
-  triggerer: string;
+  /** when true, only address comments the triggerer approved with 👍 (vs all comments) */
+  approved_only?: boolean | undefined;
 }
 
 interface ImplementPlanEvent extends BasePayloadEvent {
@@ -273,7 +273,7 @@ export interface WriteablePayload {
   /** the user's actual request (body if @pullfrog tagged) */
   prompt: string;
   /** github username of the human who triggered this workflow run */
-  triggeringUser?: string | undefined;
+  triggerer?: string | undefined;
   /** event-level instructions for this trigger type (flag-expanded server-side) */
   eventInstructions?: string | undefined;
   /** repo-level instructions (flag-expanded server-side) */