feat: add Builder-Sisyphus agent with independent toggle options (#214)

* feat: add Builder-Sisyphus agent with independent toggle options

- Add Builder-Sisyphus agent (disabled by default) for build mode
- Implement independent configuration for Builder/Planner-Sisyphus agents
- Add replace_build and replace_plan options to control agent demotion
- Update schema to support new configuration options
- Update README with comprehensive configuration documentation

Addresses #212: Users can now keep default OpenCode build mode alongside Builder-Sisyphus

* docs: add OpenCode permalinks and update multilingual README files

- Add OpenCode source code permalinks to build-prompt.ts (@see tags)
- Update README.ja.md with Builder-Sisyphus documentation
- Update README.ko.md with Builder-Sisyphus documentation
- Update README.zh-cn.md with Builder-Sisyphus documentation

Permalinks reference:
- Build mode switch: build-switch.txt
- Build agent definition: agent.ts#L118-L125
- Default permissions: agent.ts#L57-L68

---------

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/config/schema.ts

@@ -30,6 +30,7 @@ export const OverridableAgentNameSchema = z.enum([
   "build",
   "plan",
   "Sisyphus",
+  "Builder-Sisyphus",
   "Planner-Sisyphus",
   "oracle",
   "librarian",
@@ -86,6 +87,7 @@ export const AgentOverridesSchema = z.object({
   build: AgentOverrideConfigSchema.optional(),
   plan: AgentOverrideConfigSchema.optional(),
   Sisyphus: AgentOverrideConfigSchema.optional(),
+  "Builder-Sisyphus": AgentOverrideConfigSchema.optional(),
   "Planner-Sisyphus": AgentOverrideConfigSchema.optional(),
   oracle: AgentOverrideConfigSchema.optional(),
   librarian: AgentOverrideConfigSchema.optional(),
@@ -105,6 +107,10 @@ export const ClaudeCodeConfigSchema = z.object({
 
 export const SisyphusAgentConfigSchema = z.object({
   disabled: z.boolean().optional(),
+  builder_enabled: z.boolean().optional(),
+  planner_enabled: z.boolean().optional(),
+  replace_build: z.boolean().optional(),
+  replace_plan: z.boolean().optional(),
 })
 
 export const ExperimentalConfigSchema = z.object({