fix(tool.registry): tolerate failed custom tool imports

[dlukt]

What does this PR do?

Fixes #12278 12278

I let GPT-5.2 create a fix.

How did you verify your code works?

After that commit accidently landed in #12273 the tests passed.
After it was reverted they also passed.
shrug emoji

[github-actions]

Hey! Your PR title fix(tool.registry): tolerate failed custom tool imports 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

[dlukt]

I'm closing this. Too many cooks