docs: correct Agent Teams system-prompt handling (appended, not replaced)

Per the Agent Teams docs, a persona body is appended to the teammate's
system prompt as additional instructions — not a replacement. The prior
wording implied the persona owned the whole prompt, which would mislead
a persona author about what coordination instructions they inherit from
the lead (SendMessage, task-list tools, etc.).

Fixes the same inaccuracy in two locations (agents/README.md and
references/orchestration-patterns.md). Flagged in review.

agents/README.md

@@ -105,7 +105,7 @@ Why this fails:
 The personas in this repo are designed to work as Claude Code subagents and as Agent Teams teammates without modification:
 
 - **As subagents:** auto-discovered when this plugin is enabled (no path config needed). Use the Agent tool with `subagent_type: code-reviewer` (or `security-auditor`, `test-engineer`). `/ship` is the canonical example.
-- **As Agent Teams teammates** (experimental, requires `CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1`): reference the same persona name when spawning a teammate. The persona's body becomes the teammate's system prompt.
+- **As Agent Teams teammates** (experimental, requires `CLAUDE_CODE_EXPERIMENTAL_AGENT_TEAMS=1`): reference the same persona name when spawning a teammate. The persona's body is **appended to** the teammate's system prompt as additional instructions (not a replacement), so your persona text sits on top of the team-coordination instructions the lead installs (SendMessage, task-list tools, etc.).
 
 Subagents only report results back to the main agent. Agent Teams let teammates message each other directly. Use subagents when reports are enough; use Agent Teams when sub-agents need to challenge each other's findings (e.g. competing-hypothesis debugging). See [references/orchestration-patterns.md](../references/orchestration-patterns.md) for the full mapping.