The \u200B (zero-width space) in AGENT_LIST_SORT_PREFIXES leaked into
the x-opencode-agent-name HTTP header, causing invalid header errors.
Agent ordering is handled by agent-priority-order.ts via numeric order
fields and insertion order — the ZWSP prefix was redundant.
Remove crash-causing name fields from 6 agent configs (sisyphus, hephaestus,
atlas, metis, momus, prometheus). The name field approach breaks opencode
because Agent.get(agent.name) uses name as lookup key.
Add getAgentConfigKey() to agent-display-names.ts for resolving display names
back to lowercase config keys (e.g. 'Atlas (Plan Executor)' -> 'atlas').