feat(agents): add gpt-5.5 native sisyphus-junior prompt

The base prompt is category-agnostic; the actual category context (deep,
quick, ultrabrain, writing) layers on top at runtime via the
promptAppend parameter resolved by resolvePromptAppend.

Distinctive elements:
- Closing '# Category context' section explicitly telling the agent
  to read the appended block as overriding defaults on conflict
- Orchestrator-facing final-answer structure (What changed / Key
  decisions / Verification / Observations / Blockers) instead of a
  user-facing conversational close
- Sparse commentary cadence; the orchestrator synthesizes progress
  for the user, so mid-task narration is mostly noise

getSisyphusJuniorPromptSource() checks gpt-5-5 before the gpt-5.4 /
gpt-5.3-codex path so the new prompt takes precedence for gpt-5.5
deployments.

src/agents/sisyphus-junior/agent.ts

@@ -12,7 +12,7 @@
 
 import type { AgentConfig } from "@opencode-ai/sdk"
 import type { AgentMode } from "../types"
-import { isGlmModel, isGptModel, isGeminiModel } from "../types"
+import { isGlmModel, isGpt5_5Model, isGptModel, isGeminiModel } from "../types"
 import type { AgentOverrideConfig } from "../../config/schema"
 import {
   createAgentToolRestrictions,
@@ -23,6 +23,7 @@ import { getGptApplyPatchPermission } from "../gpt-apply-patch-guard"
 import { buildDefaultSisyphusJuniorPrompt } from "./default"
 import { buildGptSisyphusJuniorPrompt } from "./gpt"
 import { buildGpt54SisyphusJuniorPrompt } from "./gpt-5-4"
+import { buildGpt55SisyphusJuniorPrompt } from "./gpt-5-5"
 import { buildGpt53CodexSisyphusJuniorPrompt } from "./gpt-5-3-codex"
 import { buildGeminiSisyphusJuniorPrompt } from "./gemini"
 
@@ -38,10 +39,17 @@ export const SISYPHUS_JUNIOR_DEFAULTS = {
   temperature: 0.1,
 } as const
 
-export type SisyphusJuniorPromptSource = "default" | "gpt" | "gpt-5-4" | "gpt-5-3-codex" | "gemini"
+export type SisyphusJuniorPromptSource =
+  | "default"
+  | "gpt"
+  | "gpt-5-5"
+  | "gpt-5-4"
+  | "gpt-5-3-codex"
+  | "gemini"
 
 export function getSisyphusJuniorPromptSource(model?: string): SisyphusJuniorPromptSource {
   if (model && isGptModel(model)) {
+    if (isGpt5_5Model(model)) return "gpt-5-5"
     const lower = model.toLowerCase()
     if (lower.includes("gpt-5.4") || lower.includes("gpt-5-4")) return "gpt-5-4"
     if (lower.includes("gpt-5.3-codex") || lower.includes("gpt-5-3-codex")) return "gpt-5-3-codex"
@@ -64,6 +72,8 @@ export function buildSisyphusJuniorPrompt(
   const source = getSisyphusJuniorPromptSource(model)
 
   switch (source) {
+    case "gpt-5-5":
+      return buildGpt55SisyphusJuniorPrompt(useTaskSystem, promptAppend)
     case "gpt-5-4":
       return buildGpt54SisyphusJuniorPrompt(useTaskSystem, promptAppend)
     case "gpt-5-3-codex":