feat(rawr): add safety checks for Graphite sync with --force

[mateicanavra]

Improve Graphite rebase safety with --force flag

This PR enhances our rebase documentation and scripts to address safety concerns when using Graphite commands in non-interactive automation:

1. Adds explicit guidance to use gt sync --no-restack --force --no-interactive for automation
2. Updates rebase-daily.sh to verify local/remote trunk alignment before running gt sync --force
3. Adds safety checks to prevent accidental trunk overwrites during checkpoint operations
4. Documents cautions about running Graphite commands during merge operations

These changes help prevent potential data loss scenarios where gt sync might overwrite local trunk when it cannot fast-forward, especially in CI/automation contexts.

[mateicanavra]

• feat(rawr): add safety checks for Graphite sync with --force #26 👈 (View in Graphite)
• codex/integration-upstream-main

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