[Feat] LSP rename — symbol-table-driven file-wide rename

[ax1s-x1zz]

Context

Follow-up from #75 (B3). The token-level symbol table (xazz-compiler::symbols) gives all references of a name; textDocument/rename applies the same new name to every occurrence (definition + references) in the file.

Scope

• xazz-lsp rename: collect references_of(name) → apply substitution via range edits
• Preserve declaration sites (skip the definition span when replacing)

Acceptance

Renaming a variable updates every occurrence in the file with no false edits to other symbols.

Dependencies

#75 — symbol table already exports references.

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See docs/ROADMAP.md Track B3.