Release breaking agent-first CLI v3

[andrejguran]

Summary

• hard-cut the vendored browser SDK to 2.0.0 and the final schema-2 manifest contract
• replace raw REST fixture writes with create, createMany, updateById, and deleteById
• replace requiredSecrets and ambiguous secret commands with declarative secret modes plus explicit rotate/configure workflows
• generate new projects with the simplified SDK and secret contract

Verification

• npm test (92 tests)
• npm run typecheck
• npm run lint
• npm run build
• npm run verify:version
• packed-package install, help, init, and local validation smoke