feat(sessions): add session browsing for OpenCode and OpenClaw

Add two new session providers following the existing convention-based
pattern. OpenCode reads three-layer JSON storage, OpenClaw parses JSONL
event streams. Wire up backend dispatch, frontend filter dropdown, icon
mappings, toolbar button for OpenClaw, and i18n subtitle updates.

src-tauri/src/session_manager/mod.rs

@@ -4,7 +4,7 @@ pub mod terminal;
 use serde::Serialize;
 use std::path::Path;
 
-use providers::{claude, codex};
+use providers::{claude, codex, openclaw, opencode};
 
 #[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
@@ -40,6 +40,8 @@ pub fn scan_sessions() -> Vec<SessionMeta> {
     let mut sessions = Vec::new();
     sessions.extend(codex::scan_sessions());
     sessions.extend(claude::scan_sessions());
+    sessions.extend(opencode::scan_sessions());
+    sessions.extend(openclaw::scan_sessions());
 
     sessions.sort_by(|a, b| {
         let a_ts = a.last_active_at.or(a.created_at).unwrap_or(0);
@@ -55,6 +57,8 @@ pub fn load_messages(provider_id: &str, source_path: &str) -> Result<Vec<Session
     match provider_id {
         "codex" => codex::load_messages(path),
         "claude" => claude::load_messages(path),
+        "opencode" => opencode::load_messages(path),
+        "openclaw" => openclaw::load_messages(path),
         _ => Err(format!("Unsupported provider: {provider_id}")),
     }
 }