chore: add user details to aibridge interception list endpoint (#20397)

- Adds FK from `aibridge_interceptions.initiator_id` to `users.id`
- This is enforced by deleting any rows that don't have any users. Since
this is an experimental feature AND coder never deletes user rows I
think this is acceptable.
- Adds `name` as a property on `codersdk.MinimalUser`
- This matches the `visible_users` view in the database. I'm unsure why
`name` wasn't already included given that `username` is.
- Adds a new `initiator` field to `codersdk.AIBridgeInterception` which
contains `codersdk.MinimalUser` (ID, username, name, avatar URL)
- Removes `initiator_id` from `codersdk.AIBridgeInterception`
    - Should be fine since we're still in early access

coderd/database/migrations/testdata/fixtures/000370_aibridge.up.sql

@@ -8,7 +8,7 @@ INSERT INTO
     )
 VALUES (
         'be003e1e-b38f-43bf-847d-928074dd0aa8',
-        '30095c71-380b-457a-8995-97b8ee6e5307',
+        '30095c71-380b-457a-8995-97b8ee6e5307', -- admin@coder.com, from 000022_initial_v0.6.6.up.sql
         'openai',
         'gpt-5',
         '2025-09-15 12:45:13.921148+00'
@@ -77,3 +77,82 @@ VALUES (
         '{}',
         '2025-09-15 12:45:21.674335+00'
     );
+
+-- For a later migration, we'll add an invalid interception without a valid
+-- initiator_id.
+INSERT INTO
+    aibridge_interceptions (
+        id,
+        initiator_id,
+        provider,
+        model,
+        started_at
+    )
+VALUES (
+        'c6d29c6e-26a3-4137-bb2e-9dfeef3c1c26',
+        'cab8d56a-8922-4999-81a9-046b43ac1312', -- user does not exist
+        'openai',
+        'gpt-5',
+        '2025-09-15 12:45:13.921148+00'
+    );
+INSERT INTO
+    aibridge_token_usages (
+        id,
+        interception_id,
+        provider_response_id,
+        input_tokens,
+        output_tokens,
+        metadata,
+        created_at
+    )
+VALUES (
+        '5650db6c-0b7c-49e3-bb26-9b2ba0107e11',
+        'c6d29c6e-26a3-4137-bb2e-9dfeef3c1c26',
+        'chatcmpl-CG2s28QlpKIoooUtXuLTmGbdtyS1k',
+        10950,
+        118,
+        '{}',
+        '2025-09-15 12:45:21.674413+00'
+    );
+INSERT INTO
+    aibridge_user_prompts (
+        id,
+        interception_id,
+        provider_response_id,
+        prompt,
+        metadata,
+        created_at
+    )
+VALUES (
+        '1e76cb5b-7c34-4160-b604-a4256f856169',
+        'c6d29c6e-26a3-4137-bb2e-9dfeef3c1c26',
+        'chatcmpl-CG2s28QlpKIoooUtXuLTmGbdtyS1k',
+        'how many workspaces do i have',
+        '{}',
+        '2025-09-15 12:45:21.674335+00'
+    );
+INSERT INTO
+    aibridge_tool_usages (
+        id,
+        interception_id,
+        provider_response_id,
+        tool,
+        server_url,
+        input,
+        injected,
+        invocation_error,
+        metadata,
+        created_at
+    )
+VALUES (
+        '351b440f-d605-4f37-8ceb-011f0377b695',
+        'c6d29c6e-26a3-4137-bb2e-9dfeef3c1c26',
+        'chatcmpl-CG2s28QlpKIoooUtXuLTmGbdtyS1k',
+        'coder_list_workspaces',
+        'http://localhost:3000/api/experimental/mcp/http',
+        '{}',
+        true,
+        NULL,
+        '{}',
+        '2025-09-15 12:45:21.674413+00'
+    );