build: install gems via bundler via yarn hook

[mikehardy]

Summary

• Add yarn ruby:install (bundle check || bundle install) and run it from postinstallDev so a root yarn installs root Gemfile gems after the move to bundle exec pod.
• Reorder CI to run BUNDLE_FROZEN=true bundle install before yarn; postinstall ruby:install is then a no-op via bundle check, keeping frozen lockfile enforcement intact.
• Update OKF install docs so agents use yarn ruby:install / root yarn, not bare bundle install.

Noticed while validating e2e after rebasing onto main: fresh worktrees that only ran yarn hit Bundler::GemNotFound on the first Apple pod:install. This closes that bootstrap hole for local/dev paths analyzed while keeping CI supply-chain hardening.

• Related: build(release): update CocoaPods lockfiles during release #9208

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Maintainer note: internal tracking Fixes CPRN-367

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.06%. Comparing base (4ef21d0) to head (5065ed3).

❗ There is a different number of reports uploaded between BASE (4ef21d0) and HEAD (5065ed3). Click for more details.

HEAD has 3 uploads less than BASE

Flag	BASE (4ef21d0)	HEAD (5065ed3)
jest	1	0
e2e-ts-android	1	0
android-native	1	0

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #9215      +/-   ##
============================================
- Coverage     68.36%   62.06%   -6.30%     
============================================
  Files           516      324     -192     
  Lines         37853    24060   -13793     
  Branches       5183     3307    -1876     
============================================
- Hits          25875    14930   -10945     
+ Misses        10187     8308    -1879     
+ Partials       1791      822     -969     

Flag	Coverage Δ
android-native	?
e2e-ts-android	?
e2e-ts-ios	53.51% <ø> (ø)
e2e-ts-macos	49.68% <ø> (ø)
ios-native	68.70% <ø> (+0.01%)	⬆️
ios-ruby	100.00% <ø> (ø)
jest	?

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