feat(workflows): drop the Tool Execution Flow sankey

The d3-sankey tool-transition chart was the last of the deep harness-internals
visualizations issue #6 set out to remove: a wall of bands showing that Read
tends to precede Edit, with nothing a reader could act on. It goes, along with
its i18n keys in both locales and the now-orphaned d3-sankey dependency.

The workflows API response is untouched — `toolFlow` still ships in the
aggregate and still feeds the Dashboard's top-tools list. Remaining sections
renumber 4-9.

client/package.json

@@ -16,7 +16,6 @@
     "@xterm/addon-fit": "^0.10.0",
     "@xterm/xterm": "^5.5.0",
     "d3": "^7.9.0",
-    "d3-sankey": "^0.12.3",
     "i18next": "^26.0.8",
     "i18next-browser-languagedetector": "^8.2.1",
     "lucide-react": "^0.474.0",
@@ -30,7 +29,6 @@
     "@testing-library/react": "^16.3.2",
     "@testing-library/user-event": "^14.6.1",
     "@types/d3": "^7.4.3",
-    "@types/d3-sankey": "^0.12.5",
     "@types/react": "^18.3.18",
     "@types/react-dom": "^18.3.5",
     "@vitejs/plugin-react": "^4.3.4",