refactor(sisyphus-agent): rename Builder-Sisyphus to OpenCode-Builder and remove custom overrides

- Renamed agent from 'Builder-Sisyphus' to 'OpenCode-Builder' in schema and config
- Removed BUILD_SYSTEM_PROMPT and BUILD_PERMISSION custom overrides
- Now uses OpenCode's default build agent configuration exactly
- Simplified agent configuration to rely on OpenCode defaults

🤖 Generated with assistance of OhMyOpenCode

src/config/schema.ts

@@ -30,7 +30,7 @@ export const OverridableAgentNameSchema = z.enum([
   "build",
   "plan",
   "Sisyphus",
-  "Builder-Sisyphus",
+  "OpenCode-Builder",
   "Planner-Sisyphus",
   "oracle",
   "librarian",
@@ -87,7 +87,7 @@ export const AgentOverridesSchema = z.object({
   build: AgentOverrideConfigSchema.optional(),
   plan: AgentOverrideConfigSchema.optional(),
   Sisyphus: AgentOverrideConfigSchema.optional(),
-  "Builder-Sisyphus": AgentOverrideConfigSchema.optional(),
+  "OpenCode-Builder": AgentOverrideConfigSchema.optional(),
   "Planner-Sisyphus": AgentOverrideConfigSchema.optional(),
   oracle: AgentOverrideConfigSchema.optional(),
   librarian: AgentOverrideConfigSchema.optional(),