fix: validate registry remote OAuth secret references

[fengjikui]

Summary

• Preserve registry remote oauth_config.client_secret / bearer_token references when converting registry metadata into the remote MCP form.
• Validate secret-store references before submitting registry remote installs so missing keys show a field-level error instead of failing later in the workload API.
• Reuse the same available-secret validation in the remote MCP schema for OAuth, bearer token, top-level secret, and secret-header references.

Fixes #1067.

Validation

• pnpm exec vitest run renderer/src/features/registry-servers/lib/__tests__/orchestrate-run-remote-registry-server.test.ts renderer/src/common/lib/workloads/remote/__tests__/form-schema-remote-mcp.test.ts renderer/src/features/registry-servers/components/__tests__/dialog-form-remote-registry-mcp.test.tsx renderer/src/features/mcp-servers/components/remote-mcp/__tests__/dialog-form-remote-mcp.test.tsx renderer/src/features/mcp-servers/hooks/__tests__/use-update-server.test.tsx
• pnpm run type-check
• pnpm exec eslint common/api/registry-types.ts renderer/src/common/lib/workloads/remote/form-schema-remote-mcp.ts renderer/src/common/lib/workloads/remote/__tests__/form-schema-remote-mcp.test.ts renderer/src/features/registry-servers/lib/orchestrate-run-remote-registry-server.tsx renderer/src/features/registry-servers/lib/__tests__/orchestrate-run-remote-registry-server.test.ts renderer/src/features/registry-servers/components/dialog-form-remote-registry-mcp.tsx renderer/src/features/registry-servers/components/__tests__/dialog-form-remote-registry-mcp.test.tsx renderer/src/features/mcp-servers/components/remote-mcp/dialog-form-remote-mcp.tsx
• git diff --check