fix(opencode): guard shell permission parse failures

[nikitakot]

Issue for this PR

Closes#39931

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

PowerShell parsing can return an error tree with no command patterns, causing the shell permission check to be skipped. When the syntax tree contains errors, this change checks the raw command instead and avoids deriving a reusable approval pattern from the invalid tree.

How did you verify your code works?

• bun test test/tool/shell.test.ts --timeout 30000 -t "falls back to the raw command"
• bun typecheck
• bunx prettier --check src/tool/shell.ts test/tool/shell.test.ts

Screenshots / recordings

Not applicable.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[nikitakot]

@Hona@rekram1-node hey folks can someone have a look at it? the issue is also present in V2

tldr.: permissions should not be escaped completely when shell command parsing fails, this PR tries to fix it

[opencode-agent]

Reviewed the parse-error fallback and regression coverage. No blocking findings.