recv mcp tool: default max to a small batch of 5 (wire default stays 1)

docs/conventions.md

@@ -119,9 +119,13 @@ in `hive-c0re::dashboard_events::DashboardEvent`.
 
 `AgentRequest::Recv` is the only path that delivers messages to an
 agent. Always returns a list (`Messages { messages }`) — empty when
-nothing's pending, single-pop when `max = None` (default 1, the
-single-message behaviour), batched up to `max` when caller asks for
-more (server-side cap is 32; values above clamp silently).
+nothing's pending, single-pop when `max = None` (wire default 1),
+batched up to `max` when the caller asks for more (server-side cap
+is 32; values above clamp silently). The wire default MUST stay 1:
+the harness turn loop sends `max: None` and consumes only the first
+message, so a bigger server-side default would silently drop the
+rest of a popped batch. The agent-facing `recv` MCP tool defaults to
+`max = 5` at the tool layer instead (a small batch per call).
 `wait_seconds` long-polls for the first message; once one arrives —
 or one is already pending — the call drains up to `max` in total
 before returning, so a single `Recv` call coalesces a burst.

docs/turn-loop.md

@@ -519,7 +519,7 @@ ttl_seconds?, to?)`, `answer(id, answer)`, `ack_until(up_to)`.
   that carve-out is structural, keyed on parent relationship, not name).
 - `recv` — drain inbox. Without `wait_seconds` (or `0`) returns
   immediately. Positive value parks the turn up to that many seconds
-  (cap 180) — incoming messages wake instantly. `max` (default 1, cap
+  (cap 180) — incoming messages wake instantly. `max` (tool default 5, cap
   32) drains up to N rows; `wait_seconds` applies to the first, then
   drains up to `max` total. Each returned row is prefixed with
   `[msg #<id>]` (broker row id; note the highest id seen, then pass