client: drop unused /config fallback

[eriknordmark]

Description

Found some dead comment and dead code from a long time ago when we introduced the /uuid API endoint in the controllers.

zedclient's doGetUUID carried a comment promising a fall-back to the
legacy /config endpoint when /uuid fails. The fallback was never
wired up — only the /uuid path is reachable. This PR removes the
unreachable code and the misleading comment. No behavior change.

How to test and validate this PR

Onboard a device against any controller and confirm the device UUID is
fetched and written as before. Existing onboarding e2e in Eden covers
this path; no new test added in this PR.

Changelog notes

No user-facing changes.

PR Backports

• 16.0-stable: No.
• 14.5-stable: No.
• 13.4-stable: No.

Checklist

• I've provided a proper description
• I've written the test verification instructions

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 20.92%. Comparing base (d093be1) to head (7c9c3f3).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5954      +/-   ##
==========================================
+ Coverage   20.50%   20.92%   +0.42%     
==========================================
  Files         487      497      +10     
  Lines       90131    91771    +1640     
==========================================
+ Hits        18482    19204     +722     
- Misses      70095    70829     +734     
- Partials     1554     1738     +184     

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[rene]

@claude

[claude]

Claude finished @rene's task in 1m 15s —— View job

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Code Review

• Read PR diff and changed files
• Review code changes
• Post inline comments

No issues found. The removal is clean: all three deleted functions (parseConfig, validateConfigMessage, readConfigResponseProtoMessage), the prevConfigHash global, and the passthrough doGetUUID wrapper have zero remaining callers. The dead import removals (fmt, mime, zconfig) and the explicit uuid alias are correct. The improved docstring on parseUUIDResponse is accurate.

[rene]

LGTM - asked claude for testing the workflow....