perf: truncate content_text preview in history/search queries

GetHistory and SearchHistory selected the full content_text column for
every row, so a page of large text items serialized up to megabytes of
JSON over D-Bus and parsed it on the GJS main loop, only to render a
~140-char snippet. The client-side cut never bounded the wire cost.

Truncate to PREVIEW_CHARS (200) with substr() in SQL on both list paths.
Full content is still served on demand by GetItemContent for paste-back.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

strata-daemon/src/db.rs

@@ -4,6 +4,13 @@ use serde::{Deserialize, Serialize};
 use std::path::Path;
 use std::sync::{Mutex, MutexGuard};
 
+/// Characters of `content_text` returned as a display preview by the paginated
+/// and search list queries. The full payload is never sent over these paths --
+/// it is fetched on demand via `get_raw_item` / `GetItemContent` for paste-back.
+/// Keeping the trim in SQL means a page of large text items costs a few KB of
+/// JSON, not megabytes, and the work stays in the daemon.
+const PREVIEW_CHARS: usize = 200;
+
 /// Metadata for a clipboard entry - does NOT include thumbnail bytes.
 /// Thumbnails are fetched separately via `get_thumbnail` for lazy loading.
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -174,13 +181,14 @@ impl Db {
             return Ok(Vec::new());
         }
 
-        let mut stmt = conn.prepare(
-            "SELECT id, mime_type, content_text, source_app, created_at,
+        let sql = format!(
+            "SELECT id, mime_type, substr(content_text, 1, {PREVIEW_CHARS}), source_app, created_at,
                     thumbnail_blob IS NOT NULL AS has_thumb
              FROM clipboard_history
              ORDER BY created_at DESC
-             LIMIT ?1 OFFSET ?2",
-        )?;
+             LIMIT ?1 OFFSET ?2"
+        );
+        let mut stmt = conn.prepare(&sql)?;
 
         let items = stmt
             .query_map(params![effective_limit as i64, offset as i64], |row| {
@@ -220,14 +228,15 @@ impl Db {
         }
         let fts_query = tokens.join(" ");
 
-        let mut stmt = conn.prepare(
-            "SELECT h.id, h.mime_type, h.content_text, h.source_app, h.created_at,
+        let sql = format!(
+            "SELECT h.id, h.mime_type, substr(h.content_text, 1, {PREVIEW_CHARS}), h.source_app, h.created_at,
                     h.thumbnail_blob IS NOT NULL AS has_thumb
              FROM clipboard_history h
              WHERE h.rowid IN (SELECT rowid FROM clipboard_fts WHERE clipboard_fts MATCH ?1)
              ORDER BY h.created_at DESC
-             LIMIT ?2",
-        )?;
+             LIMIT ?2"
+        );
+        let mut stmt = conn.prepare(&sql)?;
 
         let items = stmt
             .query_map(params![fts_query, limit as i64], |row| {

strata-daemon/src/dbus_service.rs

@@ -69,8 +69,9 @@ impl StrataManager {
             })
             .map_err(|e| zbus::fdo::Error::Failed(e.to_string()))
     }
-    /// Return a page of recent items as JSON metadata (no inline thumbnail bytes).
-    /// Clients call GetThumbnail(id) lazily for items with has_thumbnail=true.
+    /// Return a page of recent items as JSON metadata (no inline thumbnail bytes,
+    /// content_text truncated to a preview). Clients call GetThumbnail(id) lazily
+    /// for items with has_thumbnail=true and GetItemContent(id) for full content.
     /// `offset` is from the most recent item (0 = newest).
     async fn get_history(&self, offset: u32, limit: u32) -> zbus::fdo::Result<String> {
         let db = self.db.clone();