sync-preview: merge main into preview

[aidandaly24]

Summary

• Real merge of main into preview — includes CDK caret fix (fix: preserve caret range for @aws/agentcore-cdk dependency #1044) and release v0.12.1 changes

⚠️ You MUST merge this PR using "Create a merge commit". NOT squash. NOT rebase.

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	43.43%	8702 / 20036
🔵	Statements	42.77%	9213 / 21537
🔵	Functions	40.95%	1468 / 3584
🔵	Branches	40.67%	5678 / 13960

Generated in workflow #2153 for commit d8b8bd3 by the Vitest Coverage Report Action

[agentcore-cli-automation]

🚨 This PR is based on a stale preview and will regress recent merges

The merge commit in this PR (d8b8bd3) has parents 01b3b7d (preview side) and 27ce126 (main side), but 01b3b7d is not the current tip of preview. Since the branch was cut, two things have landed on preview that are not included here:

1. 626872f — feat(tests): add E2E and integration tests for Harness primitive (feat(tests): add E2E and integration tests for Harness primitive #1021)
2. 352c79c — Merge pull request Release v1.0.0-preview.4 (preview) #1041 from aws/release/v1.0.0-preview.4 (bumps version to 1.0.0-preview.4 + CHANGELOG entries)

As a result, the net diff of this PR against current preview is 7 insertions / 458 deletions across 12 files (instead of just the 36-line workflow change from #1044). Merging as-is would revert:

• package.json version: 1.0.0-preview.4 → 1.0.0-preview.3
• package-lock.json accordingly
• CHANGELOG.md entries for 1.0.0-preview.4
• Delete e2e-tests/harness-bedrock.test.ts
• Delete e2e-tests/harness-e2e-helper.ts
• Delete e2e-tests/harness-gemini.test.ts
• Delete e2e-tests/harness-openai.test.ts
• Delete integ-tests/add-remove-harness.test.ts
• Revert the harness-bedrock.test.ts baseline additions in .github/workflows/e2e-tests.yml

You can confirm with:

git diff origin/preview..origin/sync-preview/merge-main-20260429-v6 --stat

Options to fix

1. Re-create the sync branch from current preview tip (352c79c) and re-merge main into it, then force-push to sync-preview/merge-main-20260429-v6. This is the cleanest fix.
2. Open a new sync PR from a fresh branch cut off current preview, and close this one.

Given the PR description says "You MUST merge this PR using 'Create a merge commit'," merging it in its current state would directly delete PR #1021's tests and the preview.4 release from the preview branch.