feat(web): fix(web): - Add FPS configuration for terminal to stop busy cycling (Issue #13899)

[jmagder]

What does this PR do?

This PR fixes #13899 and fixes #13817

When the terminal is loaded in the opencode web interface, my CPU cycles 100%. I traced this down to the terminal constantly requesting another animation frame. My monitor is 240hz so this used up an entire core forcing my computer into a higher power state.

This PR adds a new configurable setting via the web ux, to limit the max FPS of the terminal. I've set it to a default of 15 fps which uses negligible CPU. Setting it 0 uses the maximum frame rate. Anything else and it targets that frame rate.

I've added e2e tests to verify the settings are saved and applied to multiple terminals correctly.

Here is a screen shot of that UX:

Details of my analysis are in the original issue linked above.

Testing

1. Goto a fresh opencode web instance without a terminal. Examine CPU usage in the terminal or use the chrome profiler.
2. Open up the terminal. It should now be 15fps by default, and CPU usage should be minimal.
3. Type in the terminal make sure it doesn't look lagy
4. Open the settings and put it to 1fps, notice the terminal is laggy
5. Change the fps to 240 (or 0) on a machine that can support that refresh rate and watch the CPU usage spike to 100%

How did you verify your code works?

I ran the testing described above, and added tests.

[github-actions]

Hey! Your PR title feat(web) / fix(web) - Add FPS configuration for terminal to stop busy cycling (Issue #13899) 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]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.