Revert name fields from agent configs, add getAgentConfigKey reverse lookup

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').

src/agents/atlas/agent.ts

@@ -99,7 +99,6 @@ export function createAtlasAgent(ctx: OrchestratorContext): AgentConfig {
   ])
 
   const baseConfig = {
-    name: "Atlas (Plan Executor)",
     description:
       "Orchestrates work via task() to complete ALL tasks in a todo list until fully done. (Atlas - OhMyOpenCode)",
     mode: MODE,

src/agents/hephaestus.ts

@@ -633,7 +633,6 @@ export function createHephaestusAgent(
     : buildHephaestusPrompt([], tools, skills, categories, useTaskSystem);
 
   return {
-    name: "Hephaestus (Deep Agent)",
     description:
       "Autonomous Deep Worker - goal-oriented execution with GPT 5.2 Codex. Explores thoroughly before acting, uses explore/librarian agents for comprehensive context, completes tasks end-to-end. Inspired by AmpCode deep mode. (Hephaestus - OhMyOpenCode)",
     mode: MODE,

src/agents/metis.ts

@@ -311,7 +311,6 @@ const metisRestrictions = createAgentToolRestrictions([
 
 export function createMetisAgent(model: string): AgentConfig {
   return {
-    name: "Metis (Plan Consultant)",
     description:
       "Pre-planning consultant that analyzes requests to identify hidden intentions, ambiguities, and AI failure points. (Metis - OhMyOpenCode)",
     mode: MODE,

src/agents/momus.ts

@@ -197,7 +197,6 @@ export function createMomusAgent(model: string): AgentConfig {
   ])
 
   const base = {
-    name: "Momus (Plan Critic)",
     description:
       "Expert reviewer for evaluating work plans against rigorous clarity, verifiability, and completeness standards. (Momus - OhMyOpenCode)",
     mode: MODE,

src/agents/sisyphus.ts

@@ -539,7 +539,6 @@ export function createSisyphusAgent(
     call_omo_agent: "deny",
   } as AgentConfig["permission"];
   const base = {
-    name: "Sisyphus (Ultraworker)",
     description:
       "Powerful AI orchestrator. Plans obsessively with todos, assesses search complexity before exploration, delegates strategically via category+skills combinations. Uses explore for internal code (parallel-friendly), librarian for external docs. (Sisyphus - OhMyOpenCode)",
     mode: MODE,