[Feature]: Add self-test and doctor tests for web_dist_dir for using tilde (~) or $HOME which will fail Web UI from starting

Summary

Improve the fault check when using self-test and doctor

Problem statement

The problem is that the config for: web_dist_dir cannot contain any tildes (~) or variables ($HOME), as in "~/yo_mama/zeroclaw/web/dist".

We need a check for ~ or $.

Proposed solution

Make these check for ~ or $.

zeroclaw self-test
zeroclaw doctor

Non-goals / out of scope

na

Alternatives considered

none

Acceptance criteria

Make a check for ~ or $ in the web_dist_dir config.

Architecture impact

none

Risk and rollback

none

Breaking change?

No

Data hygiene checks

• I removed personal/sensitive data from examples, payloads, and logs.
• I used neutral, project-focused wording and placeholders.