Bug Description

The sessions_spawn tool schema (SessionsSpawnToolSchema) accepts streamTo as an optional parameter for ALL runtimes, including runtime="subagent" and runtime="acp" together.

However, the execute function rejects streamTo when runtime="subagent":

if (streamTo && runtime !== "acp") return jsonResult({
  error: `streamTo is only supported for runtime=acp; got runtime=${runtime}`
});

Expected Behavior

The schema should either:

1. Not include streamTo in the runtime="subagent" case (conditional schema), OR
2. Document clearly that streamTo is ignored/rejected for subagent runtime

Actual Behavior

1. Schema accepts streamTo unconditionally (no runtime-aware conditional)
2. Execute function rejects it for runtime="subagent"
3. Agents that follow the schema may include streamTo in their runtime="subagent calls, resulting in predictable errors

Schema Location

File: dist/pi-embedded-BYdcxQ5A.js, line ~22950

const SessionsSpawnToolSchema = Type.Object({
  task: Type.String(),
  runtime: optionalStringEnum(SESSIONS_SPAWN_RUNTIMES),
  streamTo: optionalStringEnum(SESSIONS_SPAWN_ACP_STREAM_TARGETS),  // ← allowed for ALL runtimes
  ...
})

Suggested Fix

Use a conditional/dependent schema so streamTo is only allowed when runtime="acp":

• When runtime === "acp" → streamTo is allowed
• When runtime === "subagent" → streamTo should be stripped or rejected at schema level

Or alternatively: strip streamTo from params before the validation check when runtime !== "acp".