fix(delegate-task): require one goal per deep call

The caller-facing description told orchestrators WHAT `deep` is but
never specified goal cardinality, so they bundled multiple goals into
one call (e.g. "fix X + merge Y + deploy Z"). The deep agent's own
prompt was already configured to refuse such bundles, but only after
they arrived. The rule now lives on the caller side: ONE goal + ONE
deliverable per call; multiple goals must fan out as parallel `deep`
calls.

docs/reference/features.md

@@ -117,7 +117,7 @@ By combining these two concepts, you can generate optimal agents through `task`.
 | -------------------- | ------------------------------- | --------------------------------------------------------------------------------------------------------------------------- |
 | `visual-engineering` | `google/gemini-3.1-pro`         | Frontend, UI/UX, design, styling, animation                                                                                 |
 | `ultrabrain`         | `openai/gpt-5.5` (xhigh)        | Deep logical reasoning, complex architecture decisions requiring extensive analysis                                         |
-| `deep`               | `openai/gpt-5.5` (medium)       | Goal-oriented autonomous problem-solving. Thorough research before action. For hairy problems requiring deep understanding. |
+| `deep`               | `openai/gpt-5.5` (medium)       | Goal-oriented autonomous problem-solving on hairy problems requiring deep research. ONE goal + ONE deliverable per call — multiple goals must fan out as parallel `deep` calls, never bundled into one. |
 | `artistry`           | `google/gemini-3.1-pro` (high)  | Highly creative/artistic tasks, novel ideas                                                                                 |
 | `quick`              | `openai/gpt-5.4-mini`           | Trivial tasks - single file changes, typo fixes, simple modifications                                                       |
 | `unspecified-low`    | `anthropic/claude-sonnet-4-6`   | Tasks that don't fit other categories, low effort required                                                                  |

src/tools/delegate-task/openai-categories.ts

@@ -203,7 +203,7 @@ export const OPENAI_CATEGORIES: BuiltinCategoryDefinition[] = [
   {
     name: "deep",
     config: { model: "openai/gpt-5.5", variant: "medium" },
-    description: "Goal-oriented autonomous problem-solving. Thorough research before action. For hairy problems requiring deep understanding.",
+    description: "Goal-oriented autonomous problem-solving on hairy problems requiring deep research. ONE goal + ONE deliverable per call — multiple goals must fan out as parallel `deep` calls, never bundled into one.",
     promptAppend: DEEP_CATEGORY_PROMPT_APPEND,
     resolvePromptAppend: resolveDeepCategoryPromptAppend,
   },