Fix hover and qualified-symbol resolution for jdtls

[briiiqtt]

Summary

The Eclipse JDT language server (jdtls) behaves differently from the servers this project was built against, which breaks hover and qualified (e.g. Foo.bar) definition/reference lookups. This reworks the affected tools to handle jdtls while degrading safely for every other server.

Hover

• Widen Hover.Contents to the spec union Or_Hover_contents so jdtls' deprecated MarkedString / []MarkedString shapes decode instead of collapsing to empty, and render all three shapes uniformly.
• Advertise hover contentFormat [Markdown, PlainText] so servers prefer MarkupContent going forward.
• Fix the empty-hover line fallback dropping text on a file's last line.

Qualified-symbol resolution

• Add a workspace/symbol + textDocument/documentSymbol fallback that resolves Foo.bar style names, scoping members to their container type (handling hierarchical and flat symbols, nested/generic containers).
• Pass server-provided names as args rather than into the format string to avoid %-verb injection; dedup members across results.

Robustness

• Route URI→path through uriToPath, recovering the panic on non-file URIs (jdt://) so all tools degrade gracefully instead of crashing.
• Unify the references error policy: skip per-file open errors but surface a hard references RPC failure only when nothing resolved.
• Fix line-number padding width off-by-one.

Tests

Adds unit tests for hover shapes, qualified resolution, container scoping, cross-result dedup, fallback wiring, and the line helpers.

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