fix(opencode): add input limit for codex-5.2

[brandon93s]

What does this PR do?

• Add support for the input limit from models.dev
• Adds dedicated input limit for codex 5.2
• Closes Default Codex context length not matching Pro plan #7705
• See openai: codex input context limit models.dev#642

How did you verify your code works?

• Tested with several large sessions via bun dev to confirm compaction triggers

[github-actions]

Hey! Your PR title openai: add input limit for codex-5.2 doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

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

No duplicate PRs found

[Copilot]

Pull request overview

This PR attempts to address the ChatGPT Pro plan's lower context limit compared to the API limit by adding an input field to the model's limit configuration for the gpt-5.2-codex model.

Changes:

• Added input: 272000 to the limit object for the gpt-5.2-codex model configuration

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[brandon93s]

If an input limit is provided, it's always the usable limit. This can be less than context - output.

[brandon93s]

Auto-compaction now triggers based on the optional input limit.

There is a separate issue (I believe with all models) where the next outgoing message can overrun context/input limits. In this scenario, the error should be caught with an auto-compaction running on thread history, and then a retry of the latest message occurring. Perhaps integrated into SessionRetry.retryable with a force auto-compaction. I won't attempt that in this PR.