chat: unified session history across Claude + OpenCode (Phase 3)

/chat's session list, transcript load, delete, and rename now span both harnesses.

- opencode-sessions.ts — REST-backed reader (OpenCode's SQLite via its HTTP API, never
  the DB): listOpenCodeSessions / loadOpenCodeSession / delete / rename, returning the
  same shapes as the Claude reader, tagged harness:'opencode'. A serve is directory-
  scoped, so listing a cwd = asking the serve rooted there. Transcript rebuild maps
  user/assistant/tool parts and drops reasoning (parity with the delta filter).
- client.ts — adds listSessions/getMessages/deleteSession/renameSession over /session/*.
- chat.ts — /sessions merges both (newest first); /sessions/:id, DELETE, and
  /title route by id shape (ses_ = OpenCode). ClaudeSessionSummary gains an optional
  `harness` tag.
- send-opencode.ts — resuming from history: when the sessionKey is itself a ses_ id,
  reuse that OpenCode session instead of creating a new one.
- SessionList.tsx — shows an "OpenCode" badge for OpenCode sessions.

Verified end-to-end against a live serve: list (5 sessions, tagged), load (transcript
rebuilt, reasoning filtered), and rename all work. Phases 1-3 complete; needs a restart.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/workspaces/officerdev/src/apps/ChatHistory/SessionList.tsx

@@ -156,7 +156,13 @@ export const SessionList = () => {
                           })}
                         </span>
                         <span>·</span>
-                        <span>{session.messageCount} msg{session.messageCount === 1 ? '' : 's'}</span>
+                        {session.harness === 'opencode' ? (
+                          <span className="rounded bg-duck-teal/10 px-1.5 py-0.5 font-medium text-duck-teal">OpenCode</span>
+                        ) : (
+                          <span>
+                            {session.messageCount} msg{session.messageCount === 1 ? '' : 's'}
+                          </span>
+                        )}
                       </div>
                     </div>
                   </button>

src/workspaces/state/src/useClaudeSessions.ts

@@ -12,6 +12,7 @@ export type ClaudeSessionSummary = {
   createdAt: string;
   updatedAt: string;
   messageCount: number;
+  harness?: 'claude' | 'opencode'; // which harness produced it (absent = claude)
 };
 
 // Display-ready message, matching the frontend ChatMessage union (rebuilt from Claude's transcript).