remove unused files

[codecov[bot]]

Codecov Report

Base: 0.00% // Head: 99.07% // Increases project coverage by +99.07% :tada:

Coverage data is based on head (b6d3ff6) compared to base (bc0672b). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #275 +/- ## ========================================= + Coverage 0 99.07% +99.07% ========================================= Files 0 22 +22 Lines 0 7282 +7282 ========================================= + Hits 0 7215 +7215 - Misses 0 50 +50 - Partials 0 17 +17 ``` | [Impacted Files](https://codecov.io/gh/ichiban/prolog/pull/275?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase) | Coverage Δ | | |---|---|---| | [engine/clause.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL2NsYXVzZS5nbw==) | `98.40% <0.00%> (ø)` | | | [engine/number.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL251bWJlci5nbw==) | `100.00% <0.00%> (ø)` | | | [engine/env.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL2Vudi5nbw==) | `98.94% <0.00%> (ø)` | | | [engine/parser.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL3BhcnNlci5nbw==) | `99.85% <0.00%> (ø)` | | | [engine/dcg.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL2RjZy5nbw==) | `100.00% <0.00%> (ø)` | | | [engine/stream.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL3N0cmVhbS5nbw==) | `100.00% <0.00%> (ø)` | | | [cmd/1pl/interpreter.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-Y21kLzFwbC9pbnRlcnByZXRlci5nbw==) | `100.00% <0.00%> (ø)` | | | [engine/vm.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL3ZtLmdv) | `88.36% <0.00%> (ø)` | | | [engine/exception.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL2V4Y2VwdGlvbi5nbw==) | `100.00% <0.00%> (ø)` | | | [engine/promise.go](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase#diff-ZW5naW5lL3Byb21pc2UuZ28=) | `100.00% <0.00%> (ø)` | | | ... and [12 more](https://codecov.io/gh/ichiban/prolog/pull/275/diff?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Yutaka+Ichibangase)

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