refactor(v2): remove trigger_credential_collection MCP tool

Drops the in-chat credential-collection flow introduced in e92b245. Agents
can no longer collect API keys via a secure modal — users must add secrets
through OneCLI directly. Keeps the OneCLI manual-approval handler and
threaded-routing work from the same commit intact.

Removed:
* container/agent-runner/src/mcp-tools/credentials.ts (MCP tool)
* src/credentials.ts (host-side modal/OneCLI pipeline)
* src/db/credentials.ts + migration 005 (pending_credentials table)
* src/onecli-secrets.ts (createSecret CLI facade, only caller was credentials.ts)
* findCredentialResponse from agent-runner DB layer
* PendingCredential types
* Four credential hooks from ChannelSetup (getCredentialForModal,
  onCredentialReject, onCredentialSubmit, onCredentialChannelUnsupported)
* Credential card/modal handling in chat-sdk-bridge (nccr/nccm prefixes,
  Modal/TextInput imports)
* credential_request text fallback in WhatsApp adapter
* request_credential system-action case in delivery.ts

Added:
* Migration 009 drops pending_credentials on existing installs.

Vercel skill now tells the agent to ask the user to register the token via
OneCLI instead of invoking the removed tool.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/index.ts

@@ -19,13 +19,6 @@ import {
   startOneCLIApprovalHandler,
   stopOneCLIApprovalHandler,
 } from './onecli-approvals.js';
-import {
-  getCredentialForModal,
-  handleCredentialChannelUnsupported,
-  handleCredentialReject,
-  handleCredentialSubmit,
-  setCredentialDeliveryAdapter,
-} from './credentials.js';
 import { routeInbound } from './router.js';
 import {
   getPendingQuestion,
@@ -93,22 +86,6 @@ async function main(): Promise<void> {
           log.error('Failed to handle question response', { questionId, err });
         });
       },
-      getCredentialForModal,
-      onCredentialReject(credentialId) {
-        handleCredentialReject(credentialId).catch((err) =>
-          log.error('Failed to handle credential reject', { credentialId, err }),
-        );
-      },
-      onCredentialSubmit(credentialId, value) {
-        handleCredentialSubmit(credentialId, value).catch((err) =>
-          log.error('Failed to handle credential submit', { credentialId, err }),
-        );
-      },
-      onCredentialChannelUnsupported(credentialId) {
-        handleCredentialChannelUnsupported(credentialId).catch((err) =>
-          log.error('Failed to handle credential channel-unsupported', { credentialId, err }),
-        );
-      },
     };
   });
 
@@ -135,7 +112,6 @@ async function main(): Promise<void> {
     },
   };
   setDeliveryAdapter(deliveryAdapter);
-  setCredentialDeliveryAdapter(deliveryAdapter);
 
   // 5. Start delivery polls
   startActiveDeliveryPoll();