[Tooling][P1] Make dev a tested integration branch

[knzeng-e]

Scope

Execute W01 from docs/backlog/implementation/W01-dev-quality-gates.md.

Outcome

Every relevant PR into dev should produce meaningful, stable checks before the next implementation sequence starts.

Acceptance

• Add pull_request and push CI coverage for dev without dropping existing main/master coverage.
• Run frontend unit/build/lint, signaling tests, API tests/typecheck, EVM contract tests, ABI drift checks, and deterministic Playwright flows with local services.
• Use Node 22 and npm ci, least-privilege workflow permissions, and no secret-dependent fork PR checks.
• Document branch protection recommendations without changing repository administration.
• Record evidence in docs/backlog/implementation/evidence/W01.md.

Local source

docs/backlog/implementation/W01-dev-quality-gates.md