chore: add must_use to 27 non-Result public functions

- constructors: KnowledgeEntity, TextChunk, Scratchpad, IngestionTask,
  Conversation, KnowledgeRelationship, Message, TextContent,
  KnowledgeEntityEmbedding, TextChunkEmbedding
- accessors: Theme::as_str, Theme::initial_theme, TaskState::as_str,
  TaskState::display_label, StorageManager::backend_kind,
  StorageManager::local_base_path, EmbeddingProvider::backend_label,
  EmbeddingProvider::dimension, EmbeddingProvider::model_code
- queries: TaskState::is_terminal, IngestionTask::can_retry,
  KnowledgeEntityType::variants, StorageManager::resolve_local_path,
  resolve_base_dir, IngestionTask::lease_duration
- helpers: Message::format_history
- builders: StorageManager::with_backend

common/src/storage/store.rs

@@ -46,6 +46,7 @@ impl StorageManager {
     ///
     /// This method is useful for testing scenarios where you want to inject
     /// a specific storage backend.
+    #[must_use]
     pub fn with_backend(store: DynStorage, backend_kind: StorageKind) -> Self {
         Self {
             store,
@@ -55,11 +56,13 @@ impl StorageManager {
     }
 
     /// Get the storage backend kind.
+    #[must_use]
     pub fn backend_kind(&self) -> &StorageKind {
         &self.backend_kind
     }
 
     /// Access the resolved local base directory when using the local backend.
+    #[must_use]
     pub fn local_base_path(&self) -> Option<&Path> {
         self.local_base.as_deref()
     }
@@ -68,6 +71,7 @@ impl StorageManager {
     ///
     /// Returns `None` when the backend is not local or when the provided location includes
     /// unsupported components (absolute paths or parent traversals).
+    #[must_use]
     pub fn resolve_local_path(&self, location: &str) -> Option<PathBuf> {
         let base = self.local_base_path()?;
         let relative = Path::new(location);
@@ -544,6 +548,7 @@ pub mod testing {
 /// Resolve the absolute base directory used for local storage from config.
 ///
 /// If `data_dir` is relative, it is resolved against the current working directory.
+#[must_use]
 pub fn resolve_base_dir(cfg: &AppConfig) -> PathBuf {
     if cfg.data_dir.starts_with('/') {
         PathBuf::from(&cfg.data_dir)

common/src/storage/types/conversation.rs

@@ -60,6 +60,7 @@ where
 }
 
 impl Conversation {
+    #[must_use]
     pub fn new(user_id: String, title: String) -> Self {
         let now = Utc::now();
         Self {

common/src/storage/types/ingestion_task.rs

@@ -33,6 +33,7 @@ pub enum TaskState {
 }
 
 impl TaskState {
+    #[must_use]
     pub fn as_str(&self) -> &'static str {
         match self {
             TaskState::Pending => "Pending",
@@ -45,6 +46,7 @@ impl TaskState {
         }
     }
 
+    #[must_use]
     pub fn is_terminal(&self) -> bool {
         matches!(
             self,
@@ -52,6 +54,7 @@ impl TaskState {
         )
     }
 
+    #[must_use]
     pub fn display_label(&self) -> &'static str {
         match self {
             TaskState::Pending => "Pending",
@@ -170,6 +173,7 @@ stored_object!(IngestionTask, "ingestion_task", {
 });
 
 impl IngestionTask {
+    #[must_use]
     pub fn new(content: IngestionPayload, user_id: String) -> Self {
         let now = chrono::Utc::now();
 
@@ -193,10 +197,12 @@ impl IngestionTask {
         }
     }
 
+    #[must_use]
     pub fn can_retry(&self) -> bool {
         self.attempts < self.max_attempts
     }
 
+    #[must_use]
     pub fn lease_duration(&self) -> Duration {
         Duration::from_secs(u64::try_from(self.lease_duration_secs.max(0)).unwrap_or(0))
     }

common/src/storage/types/knowledge_entity.rs

@@ -34,6 +34,7 @@ pub enum KnowledgeEntityType {
     // Add more types as needed
 }
 impl KnowledgeEntityType {
+    #[must_use]
     pub fn variants() -> &'static [&'static str] {
         &["Idea", "Project", "Document", "Page", "TextSnippet"]
     }
@@ -101,6 +102,7 @@ pub struct KnowledgeEntityVectorResult {
 }
 
 impl KnowledgeEntity {
+    #[must_use]
     pub fn new(
         source_id: String,
         name: String,

common/src/storage/types/knowledge_entity_embedding.rs

@@ -32,6 +32,7 @@ impl KnowledgeEntityEmbedding {
     }
 
     /// Create a new knowledge entity embedding
+    #[must_use]
     pub fn new(entity_id: &str, embedding: Vec<f32>, user_id: String) -> Self {
         let now = Utc::now();
         Self {

common/src/storage/types/knowledge_relationship.rs

@@ -21,6 +21,7 @@ pub struct KnowledgeRelationship {
 }
 
 impl KnowledgeRelationship {
+    #[must_use]
     pub fn new(
         in_: String,
         out: String,

common/src/storage/types/message.rs

@@ -21,6 +21,7 @@ stored_object!(Message, "message", {
 });
 
 impl Message {
+    #[must_use]
     pub fn new(
         conversation_id: String,
         role: MessageRole,
@@ -57,6 +58,7 @@ impl fmt::Display for Message {
 }
 
 // helper function to format a vector of messages
+#[must_use]
 pub fn format_history(history: &[Message]) -> String {
     let mut out = String::new();
     for (i, msg) in history.iter().enumerate() {

common/src/storage/types/scratchpad.rs

@@ -28,6 +28,7 @@ stored_object!(Scratchpad, "scratchpad", {
 });
 
 impl Scratchpad {
+    #[must_use]
     pub fn new(user_id: String, title: String) -> Self {
         let now = ChronoUtc::now();
         Self {

common/src/storage/types/text_chunk.rs

@@ -28,6 +28,7 @@ pub struct TextChunkSearchResult {
 }
 
 impl TextChunk {
+    #[must_use]
     pub fn new(source_id: String, chunk: String, user_id: String) -> Self {
         let now = Utc::now();
         Self {

common/src/storage/types/text_chunk_embedding.rs

@@ -41,6 +41,7 @@ impl TextChunkEmbedding {
     ///
     /// `chunk_id` is the **key** part of the text_chunk id (e.g. the UUID),
     /// not "text_chunk:uuid".
+    #[must_use]
     pub fn new(chunk_id: &str, source_id: String, embedding: Vec<f32>, user_id: String) -> Self {
         let now = Utc::now();
 

common/src/storage/types/text_content.rs

@@ -69,6 +69,7 @@ stored_object!(TextContent, "text_content", {
 });
 
 impl TextContent {
+    #[must_use]
     pub fn new(
         text: String,
         context: Option<String>,

common/src/storage/types/user.rs

@@ -55,6 +55,7 @@ impl FromStr for Theme {
 }
 
 impl Theme {
+    #[must_use]
     pub fn as_str(&self) -> &'static str {
         match self {
             Self::Light => "light",
@@ -67,6 +68,7 @@ impl Theme {
 
     /// Returns the theme that should be initially applied.
     /// For "system", defaults to "light".
+    #[must_use]
     pub fn initial_theme(&self) -> &'static str {
         match self {
             Self::System => "light",

common/src/utils/embedding.rs

@@ -78,6 +78,7 @@ enum EmbeddingInner {
 }
 
 impl EmbeddingProvider {
+    #[must_use]
     pub fn backend_label(&self) -> &'static str {
         match self.inner {
             EmbeddingInner::Hashed { .. } => "hashed",
@@ -86,6 +87,7 @@ impl EmbeddingProvider {
         }
     }
 
+    #[must_use]
     pub fn dimension(&self) -> usize {
         match &self.inner {
             EmbeddingInner::Hashed { dimension } | EmbeddingInner::FastEmbed { dimension, .. } => {
@@ -95,6 +97,7 @@ impl EmbeddingProvider {
         }
     }
 
+    #[must_use]
     pub fn model_code(&self) -> Option<String> {
         match &self.inner {
             EmbeddingInner::FastEmbed { model_name, .. } => Some(model_name.to_string()),