fix(team-mode): preserve per-category model for kind:"category" members

The shared resolveCategoryExecution path treats `agents.sisyphus-junior.model`
(plugin config) as a higher-precedence override than the category default. That
ranking is correct for plain `task(category=...)` delegations - it lets users
pin sisyphus-junior to their preferred general model - but in team-mode it
collapses every kind:"category" member onto the same model.

Hyperplan was the visible victim: skeptic/validator/researcher/architect/creative
are routed through sisyphus-junior with five distinct categories
(unspecified-low / unspecified-high / deep / ultrabrain / artistry). With any
sisyphus-junior model configured, all five resolved to that single override
model instead of their category defaults, defeating the multi-model adversarial
debate.

Strip the override at the team-mode boundary in resolveMember rather than
changing resolveCategoryExecution itself, so:
- delegate-task callers keep the existing override semantics (3 regression
  tests at tools.test.ts:2832, 2958, 3020 stay green)
- per-category user overrides (`categories[X].model`) and explicit fallback
  chains continue to apply
- only the `kind:"category"` team-mode path opts out of the global override

Lock the contract with a regression test in resolve-member.test.ts.

Generated with assistance of [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode).

src/features/team-mode/team-runtime/resolve-member.ts

@@ -51,6 +51,14 @@ function resolveSystemContent(input: {
   }) ?? ""
 }
 
+// Strip global `agents.sisyphus-junior.model` override at the team-mode boundary —
+// `resolveCategoryExecution` ranks it above category defaults (correct for plain
+// `task(category=…)`, wrong here) and would collapse every team member to the same model.
+function withoutSisyphusJuniorOverride(ctx: ExecutorContext): ExecutorContext {
+  if (ctx.sisyphusJuniorModel === undefined) return ctx
+  return { ...ctx, sisyphusJuniorModel: undefined }
+}
+
 export async function resolveMember(
   member: Member,
   ctx: ExecutorContext,
@@ -65,7 +73,7 @@ export async function resolveMember(
           category: member.category,
           subagent_type: "sisyphus-junior",
         },
-        ctx,
+        withoutSisyphusJuniorOverride(ctx),
         undefined,
         undefined,
       )