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/000385_aibridge_fks.up.sql

@@ -0,0 +1,49 @@
+-- We didn't add an FK as a premature optimization when the aibridge tables were
+-- added, but for the initiator_id it's pretty annoying not having a strong
+-- reference.
+--
+-- Since the aibridge feature is still in early access, we're going to add the
+-- FK and drop any rows that violate it (which should be none). This isn't a
+-- very efficient migration, but since the feature is behind an experimental
+-- flag, it shouldn't have any impact on deployments that aren't using the
+-- feature.
+
+-- Step 1: Add FK without validating it
+ALTER TABLE aibridge_interceptions
+    ADD CONSTRAINT aibridge_interceptions_initiator_id_fkey
+    FOREIGN KEY (initiator_id)
+    REFERENCES users(id)
+    -- We can't:
+    -- - Cascade delete because this is an auditing feature, and it also
+    --   wouldn't delete related aibridge rows since we don't FK them.
+    -- - Set null because you can't correlate to the original user ID if the
+    --   user somehow gets deleted.
+    --
+    -- So we just use the default and don't do anything. This will result in a
+    -- deferred constraint violation error when the user is deleted.
+    --
+    -- In Coder, we don't delete user rows ever, so this should never happen
+    -- unless an admin manually deletes a user with SQL.
+    ON DELETE NO ACTION
+    -- Delay validation of existing data until after we've dropped rows that
+    -- violate the FK.
+    NOT VALID;
+
+-- Step 2: Drop existing interceptions that violate the FK.
+DELETE FROM aibridge_interceptions
+WHERE initiator_id NOT IN (SELECT id FROM users);
+
+-- Step 3: Drop existing rows from other tables that no longer have a valid
+--         interception in the database.
+DELETE FROM aibridge_token_usages
+WHERE interception_id NOT IN (SELECT id FROM aibridge_interceptions);
+
+DELETE FROM aibridge_user_prompts
+WHERE interception_id NOT IN (SELECT id FROM aibridge_interceptions);
+
+DELETE FROM aibridge_tool_usages
+WHERE interception_id NOT IN (SELECT id FROM aibridge_interceptions);
+
+-- Step 4: Validate the FK
+ALTER TABLE aibridge_interceptions
+    VALIDATE CONSTRAINT aibridge_interceptions_initiator_id_fkey;

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'
+    );