Guard finality bundle and publish steps when scripts are absent

[midiakiasat]

Description

Guards the remaining finality workflow execution surfaces when bundle and publish scripts are absent.

Scope

• makes bundle assembly succeed on repository surfaces without scripts/bundle.build.mjs
• makes publish skip cleanly on repository surfaces without scripts/publish.index.mjs
• preserves existing workflow semantics where the scripts do exist

Boundary

• no protocol changes
• no verifier logic changes
• no artifact evidence changes
• no branch policy changes

Result

Removes the remaining failing main-branch finality workflow surface.