Inbound ReqResp serving is never wired into the running node

[adust09]

On main (0f5b8e5), RequestHandler's block lookup callbacks are never assigned outside of tests, so a running node cannot serve BlocksByRoot or BlocksByRange.

The three callbacks

Callback	Declared	Wired in src/?
block_by_slot_lookup	handler.py#L179	No — assigned only in test_handler.py
block_lookup (by root)	handler.py#L176	No — set_block_lookup exists but its only caller is test_live.py#L144
current_slot_lookup	handler.py#L182	Yes — from run.py#L111

LiveEventSource has no set_block_by_slot_lookup — the string by_slot does not occur in live.py at all.

Consequence

handle_blocks_by_range always takes its first branch and replies SERVER_ERROR:

leanSpec/src/lean_spec/node/networking/reqresp/handler.py

Lines 281 to 284 in 0f5b8e5

	if self.block_by_slot_lookup is None:
	logger.warning("BlocksByRange request received but no block_by_slot_lookup configured")
	await response.send_error(ResponseCode.SERVER_ERROR, "Block lookup not available")
	return

Meanwhile the client side is wired into the production path:

BackfillSync.request_blocks_by_range → SyncService → Node

So a leanSpec node issues range requests that no other leanSpec node can answer, and backfill sync between two of them cannot complete.

Note

The material for the by-root lookup already exists — signed_block_for_root reads from sync_service.store.blocks, but is passed only to ApiServer, not to the ReqResp handler.