#1181 chore(mobile): bump agent-device to 0.21.28

What and why

• Bump agent-device 0.21.25 -> 0.21.28 in @e2e-dev/mobile, @e2e-dev/limrun and docs.
• Two breaking changes in range, neither reached by e2e:
  • callstack/agent-device#3599 removes target-readiness waits (readinessTimeoutMs). e2e never passes it and polls locators itself.
  • callstack/agent-device#3547 makes SnapshotNode.ref optional. Typecheck passes.
• Notable fixes: faster Android helper captures on animating apps (callstack/agent-device#3611), Android test IME reinstall (callstack/agent-device#3606), settle quiet window (callstack/agent-device#3522).
• isUnreadableCaptureContentError (callstack/agent-device#3664) landed after 0.21.28, so #1166 keeps its local copy for now.

Verified

Ran it locally: yes - pnpm check, typecheck, mobile (273) and limrun (14) unit tests. Device behavior relies on the iOS and Android CI suites.

Checklist

• Changeset added (pnpm changeset) for any change to a published package, or the change is testbed, docs, or CI only.
• Breaking change: title carries !, the changeset body names what breaks and what replaces it, and the deprecation warning landed a window earlier (stability policy in CONTRIBUTING.md).
• Docs updated in the same PR: the docs/**/*.mdx page for the behavior, and skills/e2e/ if the skill describes it.
• Contract change: emitted .d.ts reviewed, tests/types/sdk-types.ts updated; wire change edits the schema and both fixtures.
• Engine contract change (e2e/engine): changesets for e2e, @e2e-dev/web, and @e2e-dev/mobile.