fix: address 5 edge cases from review-work findings

- C3: include command args in auto-slash-command dedup key
- H2: track completed task summaries for ALL COMPLETE message
- H9: increment tmux close retry count on re-mark
- H8: detect stale MCP connections after disconnect+reconnect race
- H8: guard disconnectedSessions growth for non-MCP sessions
- C1: await tmux cleanup in plugin dispose lifecycle

src/features/skill-mcp-manager/connection-race.test.ts

@@ -154,11 +154,11 @@ describe("getOrCreateClient disconnect race", () => {
     expect(createdClients[0]?.close).not.toHaveBeenCalled()
   })
 
-  it("#given no pending connections #when disconnectSession is called #then no errors occur and the session is added to disconnectedSessions", async () => {
+  it("#given no pending connections #when disconnectSession is called #then no errors occur and session is not added to disconnectedSessions", async () => {
     const state = createState()
 
     await expect(disconnectSession(state, "session-a")).resolves.toBeUndefined()
-    expect(state.disconnectedSessions.has("session-a")).toBe(true)
+    expect(state.disconnectedSessions.has("session-a")).toBe(false)
     expect(state.pendingConnections.size).toBe(0)
     expect(state.clients.size).toBe(0)
   })