feat: add web-worker-perf variant to libavoid-standalone demo

[kumilingus]

Summary

Adds a web-worker-perf variant to the libavoid demo and tightens the existing web-worker variant.

New perf variant (src/web-worker-perf/)

• Stress test for the worker-based router — two flowchart-style diagrams switchable via a dropdown (larger one has ~400 elements / ~450 links); routing time for each load is logged via console.time('worker routed').
• Navigation: click on blank or a cell to fit to content, drag on blank to rubber-band zoom to a region.
• The worker is terminated and recreated on each diagram switch so libavoid never carries stale state across loads.

Web-worker variant improvements

• Now shares the sample graph with the UI-thread variant via src/shared/example-graph.js, so the two apps are apples-to-apples — the only substantive difference is where the router runs. The previous web-worker/example.json is deleted.
• awaiting-update highlighter expanded to cover every pending-route state: initial load, element move/resize, new link drawn, endpoint dragged off a port. Removed per-link on routed replies (previously used a blanket removeAll).
• Filters on both directions of the wire:
  • Outbound: skip link changes that don't touch source/target, and skip endpoint moves that stay dangling (no routability change) — previously re-routed on every pointer move during a dangling drag.
  • Inbound: skip applying a routed reply to a link the user has since disconnected locally (prevents a snap-back race).
• Extracted markAwaiting / unmarkAwaiting to src/shared/awaiting.js.
• Top-of-file comments document the async architecture and message protocol.

Build / tooling

• Generalized USE_WEB_WORKERS=1 → VARIANT=<folder>. package.json keeps start-web-worker / build-web-worker working and adds matching *-web-worker-perf scripts; webpack.config.js reads process.env.VARIANT.
• AvoidRouter.onGraphReset(previousModels = []) defaults to an empty array so the perf variant's reset-from-empty flow doesn't throw.
• styles.scss: scoped .joint-paper border to .ui-thread, extended .web-worker rules to cover .web-worker-perf, added a fixed-position .diagram-selector dropdown style.

Docs

• js/README.md gains a Variants section documenting all three variants with their purpose and run commands.

Lint (pre-existing on main, bundled here to unblock CI)

• microservices-architecture/ts/src/*.ts: 68 issues auto-fixed (object-curly-spacing, @typescript-eslint/consistent-type-imports).
• microservices-architecture/ts/src/link-routing.ts: replaced (target as any)[prop] with Reflect.get(target, prop) — idiomatic for a Proxy get trap, no any cast.

Test plan

• cd libavoid-standalone-link-routing/js && npm install
• npm start — ui-thread still loads and routes the shared 5-node graph
• npm run start-web-worker — web-worker loads with the new VARIANT=web-worker env var; same graph routes through the worker; moving an element shows awaiting-update on connected links; creating a new link / dragging an endpoint off a port also flips the visual
• npm run start-web-worker-perf — perf demo loads; selector switches between Diagram 1 and Diagram 2; drag on blank rubber-band zooms; click on blank or on a cell fits the paper
• npm run lint at the repo root finishes clean

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