fix: verify mint and owner in idempotent ATA early return

[ananas-block]

Summary

• Add mint and owner validation in the idempotent ATA early return path so that an existing account for a different mint/owner is not silently accepted.

Summary by CodeRabbit

Bug Fixes

• Implemented validation checks during token account creation to verify that stored mint and owner values align with requested values. Detects and prevents mismatches, reporting failures clearly to maintain data integrity and ensure correct token account configurations.

[coderabbitai]

📝 Walkthrough

Walkthrough

This change adds runtime verification to the idempotent ATA creation path by validating that stored mint and owner match requested values. If either field mismatches, a specific error is emitted; if both match, execution continues as before.

Changes

Cohort / File(s)	Summary
ATA Creation Validation programs/compressed-token/program/src/ctoken/create_ata.rs	Added pubkey_eq import and runtime verification logic in the idempotent path to compare stored mint and owner against requested values, emitting "MintMismatch" or "OwnerMismatch" errors on failure.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Suggested labels

ai-review

Suggested reviewers

• sergeytimoshin
• SwenSchaeferjohann

Poem

🔐 A token's identity now stands guard,
Idempotent paths less scarred,
Mint and owner locked in place—
No silent mismatches win this race! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: adding verification of mint and owner values in the idempotent ATA early return path, which is the core security fix addressed in the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 70.00%.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/audit-issue-4-idempotent-ata-checks

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[ananas-block]

Superseded by #2249 which combines issues #3, #4, and #15.