Pull request overview

This PR hardens the Solana-native counter example program to fail safely on malformed instructions and unsafe account inputs, and adds regression tests intended to prevent reintroducing these footguns.

Changes:

• Avoids panics on-chain by replacing assert! with explicit error returns for readonly accounts.
• Validates instruction discriminant (including empty data) and rejects unknown instructions.
• Adds ownership validation and overflow-safe increment (checked_add) in the counter update path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
basics/counter/native/program/src/lib.rs	Adds instruction-data validation, unknown-instruction failures, owner + writable checks, and overflow-safe increment.
basics/counter/native/program/tests/test.rs	Strengthens the happy-path test and adds new failure-mode tests (unknown instruction + readonly counter).

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