feat: make reviewer-to-assignee bot dynamic with removal support

- Add pull_request_review: submitted trigger to on-review.yml so the
  workflow fires when a reviewer submits their feedback
- Split the bot into addReviewersAsAssignees / removeReviewerFromAssignees
  functions, routing by eventName + action
- Remove the MAX_ASSIGNEES=2 cap so all requested reviewers are assigned
- Mirror the existing 403 guard on the new removal path
- Update tests: drop the cap assertion, add removal flow coverage (happy
  path, no-op, 403, rethrow) and workflow_dispatch routing check

Signed-off-by: Mounil Kanakhara <mounilkankhara@gmail.com>

Author: Mounil2005

.github/scripts/__tests__/jest/bot-pr-add-reviewers-as-assignees.test.js

@@ -16,6 +16,7 @@ describe('Bot: Add Reviewers as Assignees', () => {
 
   const createTestState = () => ({
     addAssigneesCalls: [],
+    removeAssigneesCalls: [],
     pullsGetCalls: 0,
     currentPrData: null,
   });
@@ -24,6 +25,7 @@ describe('Bot: Add Reviewers as Assignees', () => {
     repo: { owner: 'hiero-ledger', repo: 'hiero-sdk-python' },
     eventName: 'pull_request_target',
     payload: {
+      action: 'review_requested',
       pull_request: {
         number: 123,
         requested_reviewers: [],
@@ -34,6 +36,21 @@ describe('Bot: Add Reviewers as Assignees', () => {
     }
   });
 
+  const createMockReviewContext = ({ reviewerLogin, assignees = [] } = {}) => ({
+    repo: { owner: 'hiero-ledger', repo: 'hiero-sdk-python' },
+    eventName: 'pull_request_review',
+    payload: {
+      action: 'submitted',
+      review: {
+        user: { login: reviewerLogin }
+      },
+      pull_request: {
+        number: 123,
+        assignees
+      }
+    }
+  });
+
   const createMockGithub = (state) => ({
     rest: {
       pulls: {
@@ -53,11 +70,17 @@ describe('Bot: Add Reviewers as Assignees', () => {
         addAssignees: async (params) => {
           state.addAssigneesCalls.push(params);
           return { data: {} };
+        },
+        removeAssignees: async (params) => {
+          state.removeAssigneesCalls.push(params);
+          return { data: {} };
         }
       }
     }
   });
 
+  // ─── Add flow ────────────────────────────────────────────────────────────────
+
   test('adds individual reviewers correctly as assignees', async () => {
     const state = createTestState();
     state.currentPrData = {
@@ -76,6 +99,23 @@ describe('Bot: Add Reviewers as Assignees', () => {
     expect(call.assignees.sort()).toEqual(['alice', 'bob']);
   });
 
+  test('adds all requested reviewers as assignees without cap', async () => {
+    const state = createTestState();
+    state.currentPrData = {
+      requested_reviewers: [{ login: 'u1' }, { login: 'u2' }, { login: 'u3' }],
+      assignees: []
+    };
+
+    const ctx = createMockContext({
+      requested_reviewers: [{ login: 'u1' }, { login: 'u2' }, { login: 'u3' }]
+    });
+
+    await handler({ github: createMockGithub(state), context: ctx });
+
+    expect(state.addAssigneesCalls).toHaveLength(1);
+    expect(state.addAssigneesCalls[0].assignees.sort()).toEqual(['u1', 'u2', 'u3']);
+  });
+
   test('ignores team reviewers', async () => {
     const state = createTestState();
     state.currentPrData = {
@@ -112,23 +152,6 @@ describe('Bot: Add Reviewers as Assignees', () => {
     expect(state.addAssigneesCalls).toHaveLength(0);
   });
 
-  test('respects MAX_ASSIGNEES = 2 cap', async () => {
-    const state = createTestState();
-    state.currentPrData = {
-      requested_reviewers: [{ login: 'u1' }, { login: 'u2' }, { login: 'u3' }],
-      assignees: []
-    };
-
-    const ctx = createMockContext({
-      requested_reviewers: [{ login: 'u1' }, { login: 'u2' }, { login: 'u3' }]
-    });
-
-    await handler({ github: createMockGithub(state), context: ctx });
-
-    expect(state.addAssigneesCalls).toHaveLength(1);
-    expect(state.addAssigneesCalls[0].assignees).toHaveLength(2);
-  });
-
   test('does nothing when no reviewers are requested', async () => {
     const state = createTestState();
     const ctx = createMockContext({ requested_reviewers: [] });
@@ -150,7 +173,7 @@ describe('Bot: Add Reviewers as Assignees', () => {
     expect(state.addAssigneesCalls).toHaveLength(0);
   });
 
-  test('supports workflow_dispatch with pr_number input', async () => {
+  test('supports workflow_dispatch with pr_number input and routes to add flow', async () => {
     const state = createTestState();
     state.currentPrData = { requested_reviewers: [{ login: 'eve' }], assignees: [] };
 
@@ -164,6 +187,7 @@ describe('Bot: Add Reviewers as Assignees', () => {
 
     expect(state.addAssigneesCalls).toHaveLength(1);
     expect(state.addAssigneesCalls[0].issue_number).toBe(128);
+    expect(state.removeAssigneesCalls).toHaveLength(0);
   });
 
   test('handles invalid pr_number in workflow_dispatch', async () => {
@@ -183,7 +207,7 @@ describe('Bot: Add Reviewers as Assignees', () => {
     }
   });
 
-  test('gracefully handles 403 permission errors', async () => {
+  test('gracefully handles 403 permission errors on add', async () => {
     const ctx = createMockContext({ requested_reviewers: [{ login: 'x' }] });
 
     const errorMock = {
@@ -194,15 +218,16 @@ describe('Bot: Add Reviewers as Assignees', () => {
             const err = new Error('Forbidden');
             err.status = 403;
             throw err;
-          }
+          },
+          removeAssignees: async () => {}
         }
       }
     };
 
     await expect(handler({ github: errorMock, context: ctx })).resolves.not.toThrow();
   });
 
-  test('rethrows non-403 errors', async () => {
+  test('rethrows non-403 errors on add', async () => {
     const ctx = createMockContext({ requested_reviewers: [{ login: 'x' }] });
 
     const errorMock = {
@@ -213,6 +238,94 @@ describe('Bot: Add Reviewers as Assignees', () => {
             const err = new Error('Internal Server Error');
             err.status = 500;
             throw err;
+          },
+          removeAssignees: async () => {}
+        }
+      }
+    };
+
+    await expect(handler({ github: errorMock, context: ctx })).rejects.toHaveProperty('status', 500);
+  });
+
+  // ─── Remove flow ─────────────────────────────────────────────────────────────
+
+  test('removes reviewer from assignees when they submit a review', async () => {
+    const state = createTestState();
+    const ctx = createMockReviewContext({
+      reviewerLogin: 'alice',
+      assignees: [{ login: 'alice' }, { login: 'bob' }]
+    });
+
+    await handler({ github: createMockGithub(state), context: ctx });
+
+    expect(state.removeAssigneesCalls).toHaveLength(1);
+    expect(state.removeAssigneesCalls[0].assignees).toEqual(['alice']);
+    expect(state.addAssigneesCalls).toHaveLength(0);
+  });
+
+  test('does not call removeAssignees when reviewer is not an assignee', async () => {
+    const state = createTestState();
+    const ctx = createMockReviewContext({
+      reviewerLogin: 'carol',
+      assignees: [{ login: 'alice' }]
+    });
+
+    await handler({ github: createMockGithub(state), context: ctx });
+
+    expect(state.removeAssigneesCalls).toHaveLength(0);
+    expect(state.addAssigneesCalls).toHaveLength(0);
+  });
+
+  test('review submitted by someone who was never a reviewer is a no-op', async () => {
+    const state = createTestState();
+    const ctx = createMockReviewContext({
+      reviewerLogin: 'outsider',
+      assignees: []
+    });
+
+    await handler({ github: createMockGithub(state), context: ctx });
+
+    expect(state.removeAssigneesCalls).toHaveLength(0);
+  });
+
+  test('gracefully handles 403 permission errors on remove', async () => {
+    const ctx = createMockReviewContext({
+      reviewerLogin: 'alice',
+      assignees: [{ login: 'alice' }]
+    });
+
+    const errorMock = {
+      rest: {
+        pulls: { get: async () => ({}) },
+        issues: {
+          addAssignees: async () => {},
+          removeAssignees: async () => {
+            const err = new Error('Forbidden');
+            err.status = 403;
+            throw err;
+          }
+        }
+      }
+    };
+
+    await expect(handler({ github: errorMock, context: ctx })).resolves.not.toThrow();
+  });
+
+  test('rethrows non-403 errors on remove', async () => {
+    const ctx = createMockReviewContext({
+      reviewerLogin: 'alice',
+      assignees: [{ login: 'alice' }]
+    });
+
+    const errorMock = {
+      rest: {
+        pulls: { get: async () => ({}) },
+        issues: {
+          addAssignees: async () => {},
+          removeAssignees: async () => {
+            const err = new Error('Internal Server Error');
+            err.status = 500;
+            throw err;
           }
         }
       }