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

Introduce Expo Router integration with a new Screens view and API to surface screens and transitions, plus a new Steps API and UI to depict typed steps from anchors or symbols. Extend codegraph’s extraction and resolution to handle namespace objects (export default NAME, two-statement forms, and default bindings) and React hook bindings for handlers, improving accuracy of flows across JS ↔ native boundaries. Add Swift/React Native bridge receiver evidence (RCT_EXTERN_MODULE, RCT_EXTERN_METHOD) and related resolution logic, with tests covering namespace-object resolution, useCallback-driven handlers, and inline RN event listeners. Update UI to include a Steps tab and associated components (StepsView, StepNode, ScreenEdge) and wire navigation to expose steps-based exploration via /api/steps and UI routes. Documentation and changelog reflect the new Expo Router integration and steps surface capabilities.

README.md

@@ -349,6 +349,7 @@ What you get on that screen:
 - Click any file path to open the **file view**: everything that file depends on, its outline in source order, and everything that depends on it. Its **Source** tab shows the whole file with the same gutter markers, plus an arc in the left margin for every call that stays inside the file — the one place a file's internal call structure is legible, because source order does the layout. A 6,800-line file scrolls at full speed.
 - **Ask for a path.** Type "how does execute reach getFile" (or `execute -> getFile`) and you get the **flow**: one card per hop, each opened at the line that makes the next call. Hops that no static edge records — a callback, an interface dispatch, a React re-render — are drawn dashed and name where the handler was wired. "Read as flow" turns a walk you did by hand into the same strip.
 - **And when the path runs out, it says where.** A flow that doesn't get there ends in "Where the graph stops": the kind of dispatch that ended it (a computed member call, a `getattr`, a reflective invoke, a message bus), its line, the key when the source spells one out, and a shortlist of what could be on the other side — plus the name-only matches CodeGraph refused to follow, with their confidence. Nothing is guessed, and a flow that does connect never shows it.
+- **What happens from here.** On an app with screens, the **Screens** tab draws one box per screen and an arrow for every way of getting from one to another, each labelled with the condition under which it happens. The **Steps** tab does the same for what happens *on* a screen: pick one (or any symbol) and you get its handlers, the calls that cross into native code, the native events that come back, the store actions it writes and the requests that leave the app, as typed steps with the plumbing between them folded into the arrows — the whole capture-to-upload flow of a React Native app on one picture, with every step a click from the next anchor or a Flow strip.
 - **The map**: the whole project at module granularity, laid out from the graph with dependencies pointing down — never drawn by hand, and the same picture every time. Cycles are listed rather than straightened away.
 - **Take the picture with you.** A flow strip or a map can be copied as an image straight into a pull-request comment, or saved as an SVG for a README — always in the light theme, whichever one you are reading in, with a caption saying what the picture is. The SVG is real text, so it stays sharp at any size and the names in it are selectable.
 - **Keep a walk.** Press **Save trail** on the trail bar, name it, and the path is kept — listed on the empty screen and on Entry points, above the suggestions, and reopened at the symbol you left with the whole walk restored. Steps are remembered by what they are, not where they sat, so a saved trail survives editing the code it describes; when something does move it says which step moved, which was renamed away, and how much of the walk still opens. Trails are plain JSON under `.codegraph/ui/trails/` (git already ignores it), and **Export** hands you the file if you would rather commit one.