gha-expression-proof 1.0.0

# Receipt Check IDs

`gha-expression-proof` receipts use stable check IDs so offline CI systems can assert on specific expression behavior.

| ID | Status | Meaning |
| --- | --- | --- |
| `expression.syntax` | pass/fail | Expression parsing succeeded or failed. |
| `expression.evaluate` | pass/fail/skip | Expression evaluation succeeded, failed, or was skipped after parse failure. |
| `expression.if.default_status` | pass/skip | `--if-condition` applied the implicit `success()` status guard. |
| `expression.hash_files` | pass/skip | `hashFiles()` was used and evaluated, or was not used. |
| `template.syntax` | pass/fail | Template parsing succeeded or failed. |
| `template.evaluate` | pass/fail | Template interpolation succeeded or failed. |

Failed checks make the CLI exit with status code `1`. Warnings are not currently emitted by the 1.0 rule set, but `--strict` is available for future-compatible gates that want warnings to be fatal.