feat(classfile): add resource schema reader

[aofei]

Add cl/outline/classfile to load resource schema from one typed framework package.

This reader collects resource kinds, discovery directives, name-discovery directives, handle-bearing types, and resource-api-scope-binding directives from Go and XGo source.

Also fix outline.NewPackage to load Go-file constant expressions when reading package outlines. This makes the schema reader work on real Go framework packages such as spx, not just on synthetic test packages.

Updates #2704

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.97%. Comparing base (df19f4a) to head (c1db598).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
cl/compile.go	60.00%	5 Missing and 1 partial ⚠️
cl/func_type_and_var.go	33.33%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2726      +/-   ##
==========================================
- Coverage   94.08%   93.97%   -0.11%     
==========================================
  Files          32       32              
  Lines       10061    10081      +20     
==========================================
+ Hits         9466     9474       +8     
- Misses        425      435      +10     
- Partials      170      172       +2     

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[gemini-code-assist]

Code Review

This pull request introduces a resource schema loading system for XGo classfiles, enabling the discovery and validation of resource kinds and API scope bindings through source-level directives. It includes the implementation of a schema loader, comprehensive tests, and a new specification document. The review feedback focuses on enhancing diagnostic quality by tracking the source positions of resource declarations, which would allow for more precise error messages when encountering duplicate types or undeclared parent kinds.