Add LSP hover integration tests

[orien]

Context

The pony-lsp tool provides LSP hover functionality but has no integration tests that exercise the full server lifecycle — only unit tests for the hover formatter exist.

Changes

• Adds _hover_integration_tests.pony: end-to-end hover tests covering classes, actors, traits, interfaces, primitives, aliases, type inference, receiver capabilities, complex types (union/tuple), generic types, and function signatures
• Adds workspace fixture files under test/workspace/hover/ used by the integration tests
• Renames _hover_tests.pony → _hover_formatter_tests.pony (and _HoverTests → _HoverFormatterTests) to distinguish the formatter unit tests from the new integration tests
• Updates test name prefixes: formatter tests use hover/formatter/*, integration tests use hover/integration/*

Considerations

All integration tests share a single _HoverWorkspaceServer actor that initializes and compiles the workspace once, then dispatches individual hover requests to each test's TestHelper. This avoids repeated compilation overhead but means tests run sequentially through one server instance.

[SeanTAllen]

Im merged this. Some thoughts on improvements to consider:

• There are no negative tests. There are no tests for "hover at this position should return null" — e.g., hovering over whitespace, a keyword like fun, or a comment. A single negative test would verify that the LSP returns null/empty hover for non-hoverable positions, which guards against false-positive regressions.
• _class.pony fixture is underutilized. The class test only hovers over the class name The fixture defines fields (field_name, mutable_field, embedded_field) and methods (simple_method, method_with_params, update_field) that aren't tested. Fields and methods are tested in other fixture files. Tje fixture is larger than the test requires. Either trim the fixture or add field/method hover checks to the class test. I'm not sure which is appropriate. I think that this plus the previous suggestion would mean "more hover checks".
• _type_inference.pony has a leading blank line. can you clean this up commit? you can push straight to main for something so minor.