fix(plugins): log silently ignored execAsRoot errors during uninstall

Plugin uninstall had two sites where execAsRoot errors were discarded:
- Skill directory removal (plugins_install.go:125) — orphaned skill dirs
  if rm -rf failed silently
- CLAUDE.md marker stripping (plugins_install_pipeline.go:326) — stale
  plugin content left in CLAUDE.md if awk script failed

Both now log the error without failing the overall uninstall (best-effort
 cleanup), giving operators visibility into incomplete uninstalls.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/handlers/plugins_install.go

@@ -171,9 +171,11 @@ func (h *PluginsHandler) uninstallViaDocker(ctx context.Context, c *gin.Context,
 			log.Printf("Plugin uninstall: skipping invalid skill name %q in %s: %v", skill, pluginName, err)
 			continue
 		}
-		_, _ = h.execAsRoot(ctx, containerName, []string{
+		if _, rmErr := h.execAsRoot(ctx, containerName, []string{
 			"rm", "-rf", "/configs/skills/" + skill,
-		})
+		}); rmErr != nil {
+			log.Printf("Plugin uninstall: failed to remove skill %s from %s: %v", skill, workspaceID, rmErr)
+		}
 	}
 
 	// 3. Delete the plugin directory itself (as root to handle file ownership).

workspace-server/internal/handlers/plugins_install_pipeline.go

@@ -417,7 +417,9 @@ func (h *PluginsHandler) stripPluginMarkersFromMemory(ctx context.Context, conta
 		`awk 'BEGIN{skip=0; blanks=0} /^%s/{skip=1; blanks=0; next} skip==1 && /^[[:space:]]*$/{blanks++; if(blanks>=2){skip=0; print; next} next} /^# Plugin: /{if(skip==1)skip=0} skip==1{next} {print}' /configs/CLAUDE.md > /tmp/claude.new && mv /tmp/claude.new /configs/CLAUDE.md`,
 		regexpEscapeForAwk(marker),
 	)
-	_, _ = h.execAsRoot(ctx, containerName, []string{"bash", "-c", script})
+	if _, awkErr := h.execAsRoot(ctx, containerName, []string{"bash", "-c", script}); awkErr != nil {
+		log.Printf("Plugin uninstall: failed to strip markers from CLAUDE.md for %s in %s: %v", pluginName, workspaceID, awkErr)
+	}
 }
 
 // regexpEscapeForAwk escapes characters that have special meaning inside an