fix: always install selected task dependencies

[0xth4nh]

What changed?

Always runs make deps from the task selected in the signer UI instead of reusing an existing shared active/evm/lib directory.

The selected task Makefile already runs the shared root deps target, which removes active/evm/lib before installing that task's BASE_CONTRACTS_COMMIT. This also handles switching between tasks in one signer UI session, so contract-deployments no longer needs to purge dependencies in make sign-task.

Checks

npx tsc --noEmit
npm run lint -- --no-cache
npm run build

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1