feat(desktop): Add desktop deep link

[Rettend]

What does this PR do?

Adds the opencode:// deep link to the desktop app.

it also works when opening specific projects with this format:
opencode://file/C:/path/to/project

this is the same format that VS Code uses.

How did you verify your code works?

i could only test on Windows, but it should work everywhere.

start opencode://file/C:/path/to/project

this opens OpenCode and adds the correct project, if the project is already open it just focuses it.

fixed #6009 and #10055

[github-actions]

Hey! Your PR title Add desktop deep link 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

[adamdotdevin]

@Brendonovich handing this one off to you; wondering if we can also support deep linking to specific sessions?