fix: stop draining queue on /clear (remove SessionEnd shim) (#2136)

* fix: stop draining queue on /clear (and on every other SessionEnd)

The SessionEnd hook was wired to session-complete on Claude Code, Gemini
CLI, the transcripts processor, the OpenCode plugin, and OpenClaw. All of
those paths called POST /api/sessions/complete, which marked the session
completed and abandoned every still-pending observation in the queue.

So typing /clear (or logging out, or quitting) wiped in-flight work that
the worker was perfectly happy to keep processing on its own.

Removed the entire shim:
- Deleted SessionEnd hook block in plugin/hooks/hooks.json
- Deleted src/cli/handlers/session-complete.ts and its registry entry
- Deleted POST /api/sessions/complete route + Zod schema in SessionRoutes
- Removed call from transcripts processor handleSessionEnd
- Removed call from opencode-plugin session.deleted handler
- Removed Gemini SessionEnd → session-complete mapping
- Removed openclaw scheduleSessionComplete + completionDelayMs + timer state
- Updated tests + comments accordingly

Explicit user-initiated deletion (DELETE /api/sessions/:id and
POST /api/sessions/:sessionDbId/complete from the viewer UI) still works
via SessionCompletionHandler.completeByDbId — that's the only path that
should drain the queue.

The worker self-completes via its SDK-agent generator's finally-block, so
no external completion call is needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* docs: clarify opencode-plugin session.deleted is in-memory cleanup only

Greptile P2: file-level header still implied session.deleted called the
worker. Now it only cleans up the local contentSessionIdsByOpenCodeSessionId
map; worker self-completes via the SDK-agent generator finally-block.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/integrations/opencode-plugin/index.ts

@@ -7,7 +7,7 @@
  * Plugin hooks:
  * - tool.execute.after: Captures tool execution observations
  * - Bus events: session.created, message.updated, session.compacted,
- *   file.edited, session.deleted
+ *   file.edited, session.deleted (in-memory cleanup only; worker self-completes)
  *
  * Custom tool:
  * - claude_mem_search: Search memory database from within OpenCode
@@ -299,16 +299,7 @@ export const ClaudeMemPlugin = async (ctx: OpenCodePluginContext) => {
 
         case "session.deleted": {
           const { event } = payload as SessionDeletedEvent;
-          const contentSessionId = contentSessionIdsByOpenCodeSessionId.get(
-            event.sessionID,
-          );
-
-          if (contentSessionId) {
-            workerPostFireAndForget("/api/sessions/complete", {
-              contentSessionId,
-            });
-            contentSessionIdsByOpenCodeSessionId.delete(event.sessionID);
-          }
+          contentSessionIdsByOpenCodeSessionId.delete(event.sessionID);
           break;
         }
       }