fix(examples): harden cache and async lifecycle

[fadi-george]

Description

One Line Summary

Key demo installs to packed bytes and prevent stale async startup state.

Details

Motivation

Linear: SDK-5125.

The shared stable tarball is retained when packed bytes are unchanged, while each demo records the tarball hash it installed. Effect-local change flags protect live subscription, permission, and user events from stale startup snapshots; cancellation and request sequencing prevent late user updates. Adapted from applicable Capacitor equivalents of OneSignal/react-native-onesignal#1985 and #1981. Metro/env cache handling was not ported.

Scope

Demo setup and lifecycle code only; SDK APIs are unchanged.

Testing

• vp test run: 179 tests pass; coverage thresholds pass.
• Focused vp check for both changed hooks: passes.
• bash -n examples/setup.sh: passes.
• Cache diagnostics verify unchanged packed bytes preserve the stable tarball inode/hash, each demo stamp equals the tarball hash, and a missing per-demo stamp reinstalls the package.
• Both examples/demo and examples/demo_pods production web builds: pass.
• Linux setup reached Android sync, which cannot invoke the repository's vpx command because only the local vp executable is available; cache behavior was isolated with a no-op sync shim.
• Full vp check has an unchanged baseline README.md formatting failure.

Checklist

• I have filled out all required sections
• PR does one thing
• No public API changes
• Automated tests pass
• Diff reviewed