Resolve JuLC library sources by fully qualified class name

[satran004]

This PR fixes the remaining library source resolution limitation where OnchainLibrar classes were indexed by simple class name. That caused collisions when different packages contained libraries with the same simple name.

Changes:

• Adds a LibrarySource model with FQCN, simple name, package name, resource path, and source.
• Resolves library sources by FQCN instead of simple class name.
• Supports Java-style resolution for explicit imports, same-package references, wildcard imports, fully-qualified static calls, and transitive library dependencies.
• Reports ambiguity when an unqualified simple name matches multiple libraries.
• Migrates compiler, annotation processor, testkit, CLI, and playground call sites.
• Updates project scanning so duplicate library simple names in different packages are preserved.
• Adds Gradle plugin validation that bundled @onchainlibrary package/type declarations match their resource path.
• Adds tests covering duplicate simple names, import precedence, wildcard imports, FQCN static calls, ambiguity diagnostics, same-package transitive discovery, and bundle validation.