feat: add logging and error handling for wellknown config

[elithrar]

Adds debug logging and error handling for .well-known/opencode config fetches in enterprise installs.

Logs output both the config path (not present today) and a SHA-256 of the config so you can identify what version of the config is being pulled (or was, historically, when someone shares logs!) for a user.

Example log output with --print-logs:

DEBUG service=config url=https://opencode.example.com/.well-known/opencode fetching wellknown config
DEBUG service=config url=https://opencode.example.com/ hash=4142764bad628c8c8883665f9b17b4b32af24cb7ca9d4d4da57f85cc5ca21c18 loaded wellknown config

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Duplicate PR Search Results

No duplicate PRs found. The PR you're checking (feat: add logging and error handling for wellknown config) appears to be unique.

Related PR (Not a duplicate):

• PR feat: add experimental support for remote skills and commands via wellknown #6782: "feat: add experimental support for remote skills and commands via wellknown"
  • This PR is related in that it also deals with wellknown functionality, but it addresses a different feature (remote skills/commands support) rather than logging and error handling.

Conclusion: This PR appears to be a new feature addressing visibility, error resilience, and debugging capabilities for enterprise wellknown config fetches. No conflicting or duplicate work was found in open PRs.

[elithrar]

Rebased this and refactored since some of this was handled in #7141