Allow writes to /tmp by default without permission prompt

[remorses]

Currently opencode prompts for permission when the model writes to /tmp. Models frequently use /tmp for temporary files during tasks, and requiring approval adds friction without meaningful security benefit since /tmp is ephemeral and outside the user's project.

Writes to /tmp (and $TMPDIR) should be allowed by default.

Related: #4743

[rekram1-node]

Yeah agree, lets allow it

[remorses]

I can open a PR if you want

[rekram1-node]

yeah ill merge it

afk rn but when i get back ill look

[remorses]

Clsoing. Now you can pass in opencode.json

  "permission": {
    "edit": "allow",
    "bash": "allow",
    "external_directory": {
      "*": "ask",
      "/tmp": "allow",
      "/tmp/*": "allow",
      "/private/tmp": "allow",
      "/private/tmp/*": "allow",
      "env:$TMPDIR": "allow",
      "env:$TMPDIR/*": "allow"
    },

  },