feat(desktop): Improve keyboard navigation and add accept button in open project dialog

[razzeee]

Issue for this PR

Closes #38338

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

The Open Project dialog immediately resolved and closed when clicking a suggestion or pressing Enter, making it impossible to navigate into a subdirectory and continue. There was also no explicit confirm action.

• Tab and Enter now navigate into the highlighted directory (appends / and refetches) instead of confirming
• Clicking an item also navigates in rather than immediately opening the project
• Added Cancel and Select Folder buttons the footer
• Ctrl/Option+Enter or the button confirms the current path
• Enter with no item highlighted confirms the current filter path directly

How did you verify your code works?

Tested locally: typed a partial path, navigated into suggestions with Enter and Tab, confirmed with the button and Ctrl+Enter. Verified backspace works normally in the input.

Screenshots / recordings

Screencast.From.2026-07-22.17-50-17.mp4

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title Improve keyboard navigation and add accept button in open project dialog 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.

[BongHwi]

This also affects opencode web, not only desktop. The web path uses the same DialogSelectDirectory, where selecting a row resolves immediately and Tab is the only way to descend, which is undiscoverable on desktop and unusable on touch.
I tried to rebase this onto current dev: the only conflict is the import hunk, and onSelect hasn’t changed upstream since the branch point.
Happy to open a rebased PR if that’s easier for you.

[razzeee]

Feel free to rebase