tutorial: Optimize proposal part handling logic in received_proposal_part

[romac]

Summary

The current implementation checks for full proposal before validating height, which is inefficient as outdated parts are still being inserted into the map.

    pub fn received_proposal_part(
        &mut self,
        from: PeerId,
        part: StreamMessage<ProposalPart>,
    ) -> Option<ProposedValue<TestContext>> {
        let sequence = part.sequence;

        // Check if we have a full proposal
        let parts = self.streams_map.insert(from, part)?;

        // Check if the proposal is outdated
        if parts.height < self.current_height {

Action items

• Reorder checks to validate height before inserting into streams_map

        // Check if the part is outdated
        if part.height < self.current_height {
            debug!(
                height = %self.current_height,
                round = %self.current_round,
                part.height = %parts.height,
                part.round = %parts.round,
                part.sequence = %part.sequence,
                "Received outdated proposal part, ignoring"
            );

            return None;
        }

        // Check if we have a full proposal
        let parts = self.streams_map.insert(from, part)?;

        // Re-assemble the proposal from its parts
        let value = assemble_value_from_parts(parts);

        self.undecided_proposals
            .insert((value.height, value.round), value.clone());

        Some(value)
    }

[varun-doshi]

I'd like to take this one

[romac]

@varun-doshi Awesome, thank you!