fix: OpenCode sessions empty — SQLite OFFSET without LIMIT is syntax error

OFFSET requires LIMIT in SQLite. When session_service passes limit=None
to load all sessions for archive filtering, the generated SQL
"ORDER BY ... OFFSET 0" silently fails. Fix: use LIMIT -1 OFFSET n.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: voidcraft-dev

src-tauri/src/platforms/opencode.rs

@@ -46,7 +46,7 @@ impl super::PlatformAdapter for OpenCodePlatform {
                 l, offset
             ),
             None => format!(
-                "SELECT id, title, directory, time_updated FROM session ORDER BY time_updated DESC OFFSET {}",
+                "SELECT id, title, directory, time_updated FROM session ORDER BY time_updated DESC LIMIT -1 OFFSET {}",
                 offset
             ),
         };