ci: automate foundry-cli AUR publishing

[anandpant]

Changes

• Isolate Foundry CLI bumps; validate .SRCINFO and the release checksum manifest before automatic PAT-backed squash merge, which triggers AUR publishing.
• Exclude Foundry CLI from rolling bumps; add no-op/downgrade guards, draft dry runs, and package-targeted publish recovery.

Checks

• actionlint, ShellCheck, and repository validation passed, including lifecycle and checksum regressions.
• Live v0.0.56 checksum manifest matched. After merge: GitHub v0.0.56 no-op and v0.0.55 draft dry-run; no AUR publication.

Part of shpitdev/foundry-cli#829.