fix: accept boolean values for permission config

[itstrivial]

Fixes #7810

What does this PR do?

Users may now use boolean true/false instead of "allow"/"deny" for permissions.
This adds a preprocess step to convert booleans automatically, consistent with how tools config already handles this.

How did you verify your code works?

I created .opencode/agent/testing.md with the following permissions:

---
description: Test agent
mode: subagent
tools:
  read: true
permission:
  write: false
---

I then launched OpenCode in my project directory. It now launches successfully and does not hang like before.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[itstrivial]

The original issue #7810 also mentions poor error visibility.

This PR fixes the crash for true/false, but error messages for other invalid config values still don't display clearly.

One potential solution would be to enhance the worker thread error handlers in packages/opencode/src/cli/cmd/tui/worker.ts to format errors using FormatError() and display them via console.error():

process.on("unhandledRejection", (e) => {
  const formatted = FormatError(e)
  Log.Default.error("rejection", {
    e: e instanceof Error ? e.name : e,
    formatted,
  })
  if (formatted) console.error(formatted)
})

process.on("uncaughtException", (e) => {
  const formatted = FormatError(e)
  Log.Default.error("exception", {
    e: e instanceof Error ? e.name : e,
    formatted,
  })
  if (formatted) console.error(formatted)
})

However, I'm not sure if maintainers would prefer this approach, so I did not implement it.