feat(performance-monitor-plugin): expand data coverage

[burczu]

Closes #249.

Summary

Closes three gaps in @rozenite/performance-monitor-plugin's coverage of react-native-performance:

• react-native-mark entries — added a new React Native Marks tab. These are the native-runtime startup taxonomy (nativeLaunchStart, runJSBundleStart, …) emitted on the native side. The observer uses buffered: true so startup entries flushed before the user clicks Start Session still reach the panel.
• resource entries — added a new Resources tab. Table shows Name / Type / Duration / Size. The DetailsSidebar renders the full PerformanceResourceTiming breakdown: sizes (transfer / encoded body / decoded body), all 12 timing phases, plus optional serverTiming / workerTiming arrays.
• mark.detail preservation — the runtime previously dropped detail when serializing marks (while the UI already expected it). The serializer now includes it end-to-end; the Mark Details sidebar now renders the payload.

Architecture

The PR extracts each observer's inline serializer into a named pure function (serializeMark, serializeMeasure, serializeMetric, serializeReactNativeMark, serializeResource) in a new src/react-native/serialize.ts. Tests pin every serializer's field-copy contract, with extra coverage on serializeResource — its 20-field copy is the place a typo would silently land an undefined in the sidebar.

The plugin had no test surface before this PR. Vitest is wired in via a single test script in package.json; the runner itself was already in the workspace root devDeps.

Wire format is the existing per-type append pattern: appendResources and appendReactNativeMarks join appendMeasures / appendMarks / setMetrics. No new dependencies on the plugin.

Test plan

Automated (15 tests, up from 0):

• serialize.test.ts (15 tests): mark / measure / metric / react-native-mark / resource — field copy, mark.detail regression, string-valued metric, exhaustive ResourceTiming fixture pinning every one of ~20 fields, explicit assertion that sub-phase timing fields are not clock-shifted, optional initiatorType / secureConnectionStart undefined branches.
• pnpm --filter @rozenite/performance-monitor-plugin test — 10/10 passing.
• pnpm --filter @rozenite/performance-monitor-plugin typecheck — clean.
• pnpm --filter @rozenite/performance-monitor-plugin lint — 0 warnings.

Manual (playground, performance-monitor screen):

• Fire Network Request button (new): calls setResourceLoggingEnabled(true) on mount, then a fetch() on click — resource timing appears on the Resources tab.
• Complex Performance Scenario (existing button, enhanced): now also fires a fetch in parallel with marks/measures so the umbrella demo exercises every tab.
• Start Session on a fresh app launch — React Native Marks tab populates with native startup entries automatically (buffered: true is load-bearing here).
• mark.detail regression: fire a mark with a detail payload, click into it in the Marks tab — sidebar shows the payload.
• Export Data modal includes two new cards (React Native Marks, Resources) with their counts. Toggling them in/out of the export round-trips through the JSON.

Playground change

The PR touches apps/playground/src/app/screens/PerformanceMonitorScreen.tsx so the new tabs can be exercised without writing app code:

• setResourceLoggingEnabled(true) on mount.
• New "Fire Network Request" button (fetch('https://jsonplaceholder.typicode.com/posts/1')).
• "Complex Performance Scenario" runs a fetch in parallel.
• Screen content wrapped in a ScrollView so the now-taller screen is fully reachable.
• Instructions note that React Native Marks come from the native runtime and need no button.

Out of scope

• No version field in the export schema. The change is purely additive (new fields/counts) and existing consumers ignore unknown fields. Versioning is a separate concern best introduced when an actual breaking change is on the table.
• No UI behavior tests (RTL/jsdom). The plugin has none today; standing the infrastructure up for this feature alone would expand scope. The serializer extraction means the data-shape contracts are already pinned by unit tests.
• No new buttons to manually emit react-native-marks from JS — the lib's addEntry is not part of the public API, so manual emission would require hacks. Native startup entries cover the test case naturally.