feat: initialize server structure and database schema

- Added initial server setup with Cargo.toml defining dependencies and project structure.
- Created build.rs for generating protobuf bindings and validating wire contracts.
- Established database schema with initial migration files for conversations, messages, and runs.
- Introduced tools and prompts for Cursor functionality, enhancing user interaction capabilities.

server/src/model/message.rs

@@ -0,0 +1,165 @@
+//! Defines canonical append-only Conversation Messages.
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+use super::{ToolImageReference, ToolRoundId};
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum Role {
+    System,
+    User,
+    Assistant,
+    Tool,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
+#[serde(rename_all = "snake_case")]
+pub enum Origin {
+    Prompt,
+    User,
+    Runtime,
+    Assistant,
+    Tool,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct ToolCallContent {
+    pub index: usize,
+    pub call_id: String,
+    pub name: String,
+    pub arguments: Value,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct ToolResultContent {
+    pub call_id: String,
+    pub name: String,
+    pub content: String,
+    pub is_error: bool,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub image: Option<ToolImageReference>,
+    #[serde(skip)]
+    pub provider_parts: Vec<ContentPart>,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct ProviderReplayState {
+    pub provider_kind: String,
+    pub value: Value,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum ContentPart {
+    Text {
+        text: String,
+    },
+    Image {
+        mime_type: String,
+        #[serde(with = "base64_bytes")]
+        data: Vec<u8>,
+    },
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+#[serde(tag = "kind", rename_all = "snake_case")]
+pub enum MessageContent {
+    Parts {
+        parts: Vec<ContentPart>,
+    },
+    Assistant {
+        text: String,
+        thinking: String,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        tool_round_id: Option<ToolRoundId>,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        replay_state: Option<ProviderReplayState>,
+        tool_calls: Vec<ToolCallContent>,
+    },
+    ToolResult(ToolResultContent),
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
+pub struct CanonicalMessage {
+    pub message_id: String,
+    pub role: Role,
+    pub origin: Origin,
+    pub content: MessageContent,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub runtime_event_id: Option<String>,
+}
+
+impl CanonicalMessage {
+    pub fn text(
+        message_id: impl Into<String>,
+        role: Role,
+        origin: Origin,
+        text: impl Into<String>,
+    ) -> Self {
+        Self {
+            message_id: message_id.into(),
+            role,
+            origin,
+            content: MessageContent::Parts {
+                parts: vec![ContentPart::Text { text: text.into() }],
+            },
+            runtime_event_id: None,
+        }
+    }
+
+    pub fn parts(
+        message_id: impl Into<String>,
+        role: Role,
+        origin: Origin,
+        parts: Vec<ContentPart>,
+    ) -> Self {
+        Self {
+            message_id: message_id.into(),
+            role,
+            origin,
+            content: MessageContent::Parts { parts },
+            runtime_event_id: None,
+        }
+    }
+}
+
+mod base64_bytes {
+    use base64::{engine::general_purpose::STANDARD, Engine};
+    use serde::{Deserialize, Deserializer, Serializer};
+
+    pub fn serialize<S>(data: &[u8], serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.serialize_str(&STANDARD.encode(data))
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<u8>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let encoded = String::deserialize(deserializer)?;
+        STANDARD.decode(encoded).map_err(serde::de::Error::custom)
+    }
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
+pub struct RuntimeEvent {
+    pub event_id: String,
+    pub text: String,
+}
+
+impl RuntimeEvent {
+    pub fn into_message(self) -> CanonicalMessage {
+        CanonicalMessage {
+            message_id: format!("runtime:{}", self.event_id),
+            role: Role::User,
+            origin: Origin::Runtime,
+            content: MessageContent::Parts {
+                parts: vec![ContentPart::Text { text: self.text }],
+            },
+            runtime_event_id: Some(self.event_id),
+        }
+    }
+}