* fix(sandbox): restore saved thread files when creating E2B sandboxes
After an E2B sandbox expires between turns, a replacement starts without
the thread files already saved by the Gateway, so later reads fail.
Restore owner-scoped workspace, uploads, outputs and ACP files before a
new sandbox becomes available. Keep live sandbox reuse unchanged, share
the existing upload budget, and discard incomplete sandboxes on restore
failure. Skip links and unpublished temporary files during restoration.
Add offline regressions for release, expiry and recreation, sync and async
acquisition, owner isolation, live reuse, upload limits and failure cleanup.
* fix(sandbox): make thread restore failures actionable
* fix(sandbox): use neutral upload limit diagnostics
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Co-authored-by: conghua1013 <16472796+conghua1013@users.noreply.github.com>