Function projected_entry_count 

pub fn projected_entry_count(messages: &[ConversationMessage]) -> usize

Count the conversation entries a transcript projects into, without materializing them. One entry per chat message; an assistant tool-call message contributes its non-empty text plus one entry per call; a tool result folds into the entry of a call still awaiting a result (FIFO by tool_call_id) and otherwise counts as its own orphan entry.

The ACP session store maintains a persisted per-session counter with the same semantics. Runtime projection (conversation_message_entries) and this function are two expressions of one counting rule and must agree on every input.