Reflection follow-up: enforce pnpm lint in sub-agent coding spec template

On 2026-06-16, 2 of 3 parallel coding sub-agents (ALL-1871, ALL-1874) shipped PRs with biome format errors despite POST-PUSH-PROTOCOL Phase 1 explicitly mandating `pnpm lint` before push. Parent caught both in CI watch and fixed (commits 183528b1eb, ad251eb28f). The fix belongs upstream: the coding sub-agent spec template (the task prompt the heartbeat sends) needs a mandatory pre-push step: `cd <workspace-dir-of-changes> && pnpm lint && fix-anything-it-flags-before-pushing`. Without it, the format-failure pattern will recur on every parallel batch. Deliverables: 1. Find where the sub-agent task prompt template lives for coding sub-agents (likely in HEARTBEAT.md spawn block, AGENTS.md Phase 2, or a bin script). 2. Add an explicit mandatory pre-push step naming `pnpm lint` (or `biome check`) and a verification line: "If lint fails, FIX IT, do not push." 3. Test on the next parallel batch — should see zero biome format CI failures.