chore(release): prepare KsADK 0.7.0 public candidate

[AgentArcLab]

Summary

• publish the reviewed KsADK 0.7.0 clean export from internal source commit e8669aa4f1c765ee5059f0e91081958f2dade00a
• add checkpoint resume, resilient sessions, LangChain/LangGraph streaming compatibility, and refreshed CLI/TUI behavior
• consume @kingsoftcloud/ksadk-web@0.2.18 and update public docs and release notes

Verification

• internal full suite: 1681 passed, 6 skipped
• make public-preflight
• make public-build-alias-check
• publication pre-publish check for ksadk==0.7.0 and agentengine-sdk-python==0.7.0
• source, wheel, sdist, and alias audits: 0 violations
• make public-publish-gate

Release Boundary

• this PR only updates the public source candidate
• no tag, GitHub Release, PyPI publication, or Pages deployment is performed by this PR
• staging Hosted E2E remains required before the 0.7.0 release workflow is approved