fix: no edition warning when scratch org uses snapshot @W-22694430@

[WillieRuemmele]

Summary

• When creating a scratch org from a snapshot (no edition field), a spurious Zod validation warning was emitted: "edition: Invalid input: expected string, received undefined"
• Root cause: edition was the only non-optional field in ScratchOrgDefSchema, so safeParse always failed for snapshot-based definitions
• Fix: make edition optional in the schema with an object-level refinement that requires edition unless snapshot is present

Fixes forcedotcom/cli#3562

Work Item

@W-22694430@: Incorrect warning when creating a scratch org from snapshot

Proof of Work

• Tests: 125 scratch org tests passing, 53 schema tests passing, 57 NUT tests passing
• Lint: clean (no new warnings)
• Type check: clean
• Build: clean (pre-push hooks verified)

Real-World Testing

Linked the built library into plugin-org and tested sf org create scratch end-to-end:

Scenario	Before (bug)	After (fix)
Snapshot def (no edition)	Warning: edition: Invalid input: expected string, received undefined	No warning
Valid edition def	No warning	No warning
Invalid edition value	Proper warning with valid options	Proper warning with valid options
Empty def (no edition, no snapshot)	Generic "expected string, received undefined"	Improved: "edition is required unless creating from a snapshot"

Validation

• Per-task adversarial review: 1 medium finding (empty def regression) — resolved by adding object-level .refine()
• Integration: all checks pass (unit, NUT, lint, typecheck, build)

Test plan

• Create a scratch org from a snapshot definition (no edition field) — no warning emitted
• Create a scratch org with an edition field — validation still works (invalid editions rejected)
• Create a scratch org with neither snapshot nor edition — improved warning message
• (Manual) Create a scratch org from a real existing snapshot — confirm successful creation

[soridalac]

QA notes:
✅ Scratch org from snapshot: no warnings
✅ Edition + snapshot: throws correct error Error (orgSnapshot): Org snapshots don't support one or more options you specified: edition
✅ Lowercase edition: no warnings
✅ Uppercase edition: no warnings

[soridalac]

The nut test failings not relate to this PR.