fix(handlers): break the cycle between the entry and the handlers

[skjnldsv]

main is red: #8 and #10 were each green on their own branch and fail together.

Registering the built-in handlers on import (#8) made the entry call into lib/models, which imports registerHandler back from the entry. Entering the graph through a model rather than through the entry — which the preview-provider specs from #10 do — then reaches the entry mid-evaluation and calls a handler module whose body has not run:

Cannot access '__vite_ssr_import_2__' before initialization

The registry, the file actions and IHandler move to lib/handlers.ts, which the models import instead. The entry keeps every export it had and is now only what it does on import: offer this copy as a candidate, hold the service, register the defaults.

The regression test imports lib/models/images.ts first and registers from there; it throws the above without the split.

👾 This pull request was assisted by Claude Code, commits carry an Assisted-by trailer.

[codecov]

Codecov Report

❌ Patch coverage is 89.58333% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.37%. Comparing base (37e69a1) to head (f4a0980).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/handlers.ts	88.97%	14 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #11      +/-   ##
==========================================
+ Coverage   72.03%   72.37%   +0.34%     
==========================================
  Files          33       34       +1     
  Lines        2285     2299      +14     
  Branches      377      380       +3     
==========================================
+ Hits         1646     1664      +18     
+ Misses        633      629       -4     
  Partials        6        6              

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