feat(expo-router): add Expo Router support for Screens and navigations and introduce Steps API

- Adds Expo Router integration with a new Screens view and a Steps API to surface screens and their transitions.
- Extends codegraph extraction/resolution to handle namespace objects, React hook bindings for handlers, and Swift RN bridge evidence; introduces per-site guard arguments and trigger metadata, enabling richer flow analysis across JS ↔ native boundaries.
- Introduces UI and data-model changes to represent conditions as words (WHEN/AND/OR/NOT), display per-site call arguments, and show what fires a site (triggers). Adds new utilities (ui/conditions.ts) and updates ScreensView and StepsView to render scenarios with multiple sites and “ways” counts.
- Implements site readers for WHEN/ARGS/TRIGGER, and wiring to expose steps via API endpoints (including /api/steps); enhances tests to cover namespace resolution, useCallback-driven handlers, and inline RN event listeners.
- Updates styling and templates to reflect the new wording, scenario rows, and per-site details, including NOT instead of leading negation strings and multi-way links.
- Documents and reflects changes in changelog and design docs to describe Expo Router integration and the Steps surface.

__tests__/ui-screens-model.test.ts

@@ -190,7 +190,7 @@ describe('edgeLabel', () => {
     const collect = edgeLabel([link('/home', '/capture/collect', `${chain}guide.dontShowAgain.captureGuide`)]);
     const intro = edgeLabel([link('/home', '/guide', `${chain}!guide.dontShowAgain.captureGuide`)]);
     expect(collect).toBe('…guide.dontShowAgain.captureGuide');
-    expect(intro).toBe('…!guide.dontShowAgain.captureGuide');
+    expect(intro).toBe('…NOT guide.dontShowAgain.captureGuide');
     // The whole point: two arms of a fork no longer read the same.
     expect(collect).not.toBe(intro);
   });