Reuse local iOS builds and cancel superseded PR checks

[Xget7]

Repeated development sessions can create separate iOS Derived Data trees for the same app, while repeated pushes to a pull request keep obsolete CI runs consuming runners.
The example now reuses its local build directory, and CI cancels checks for superseded PR commits.

• Pin the example iOS scripts to ios/build/dd with ONLY_ACTIVE_ARCH=YES for local builds, add ios:build, and document Debug and isolated-directory overrides.
• Add shared build-storage guidance in AGENTS.md, imported by CLAUDE.md.
• Group PR checks by workflow and PR number in the six monorepo check workflows and the React Native mirror template.
  Push runs use commit-specific groups so every main commit can satisfy the release and mirror gates.
• Run Python harness regressions in an independent Android workflow job, providing feedback without waiting for the Android build.
• Retain CI AAR artifacts for 14 days.

Validation:

• python3 -m unittest discover -s scripts/tests: 36 tests passed without native compilation.
• actionlint 1.7.12: syntax and expressions passed for all eight root workflows plus the React Native mirror contract template; optional ShellCheck and Pyflakes integrations were disabled.
• Both iOS CLI commands passed help and installed-CLI option parsing checks, including build-directory, Debug, and architecture overrides.
• git diff --check passed.

Native builds, npm run check (TypeScript output and Codegen), and device QA were intentionally skipped at the user's request.
No simulator, emulator, or physical device was used.
Configuration checks do not establish GitHub scheduling behavior or native runtime behavior; regular PR CI remains responsible for remote build verification.