feat(code-actions, document-symbols): add more code actions and support for structs in document symbols

[roife]

• Add struct document symbols for typedef struct/union declarations, including nested generate/block scopes, and map them to LSP STRUCT.
• Add assists:
  • reformat_number_literal
  • convert_named_port_connection_shorthand
  • convert_always_block
  • convert_port_declarations
  • remove_parentheses
  • merge_nested_if
  • extract_variable
  • pull_assignment_up
  • pull_assignment_down
• Add assists description in comments

[github-actions]

Docs preview: https://vide.pascal-lab.net/preview/pr-239/

[Copilot]

Pull request overview

This PR expands the IDE/LSP feature set by adding several new code actions (assists) and enhancing document symbol support so typedef struct/union declarations are surfaced as STRUCT symbols in LSP clients. It also updates the supporting plumbing (i18n keys, LSP title mapping, test utilities, and some HIR/display helpers) to make these features discoverable and testable.

Changes:

• Add multiple new code action handlers (e.g., extract variable, remove redundant parentheses, convert always blocks, convert port declarations, merge nested if, pull assignment up/down) plus extensive unit/integration tests.
• Improve document symbols: introduce SymbolKind::Struct, map it to LSP STRUCT, and add coverage for typedef struct/union (including nested generate scopes).
• Extend localization/i18n and code-action title key mapping for newly added actions.

Reviewed changes

Copilot reviewed 41 out of 41 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/tests.rs	Test helpers for precise range selection in code action requests; enable REFACTOR_EXTRACT capability in client caps.
src/lsp_ext/to_proto.rs	Map SymbolKind::Struct to LSP STRUCT; add i18n title-key routing for new code actions.
src/i18n/en.toml	Add English strings for new code actions (incl. digit separator removal).
src/i18n/zh-CN.toml	Add/adjust Chinese strings for new code actions and refine De Morgan descriptions.
src/i18n.rs	Add i18n key constants for newly introduced code actions.
crates/slang/bindings/rust/ast.rs	Add only_children() helpers on list wrappers for “exactly one child” extraction.
crates/ide/src/verilog_2005.rs	Add document symbol regression test for typedef struct/union (including nested generate).
crates/ide/src/rename.rs	Adjust same-name port-connection handling using token value_text() comparisons.
crates/ide/src/lib.rs	Add SymbolKind::Struct variant.
crates/ide/src/document_symbols.rs	Emit struct-related document symbols and treat typedef’d structs as Struct kind.
crates/ide/src/code_action/tests.rs	Add many new unit tests; introduce selection-range test utilities.
crates/ide/src/code_action/handlers.rs	Register new code action handlers.
crates/ide/src/code_action/context.rs	Minor formatting-only change.
crates/ide/src/code_action/handlers/wrap_statement_in_begin_end.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/split_declaration_declarators.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/sort_named_instantiation_items.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/remove_parentheses.rs	New assist: remove redundant parentheses with precedence/associativity rules.
crates/ide/src/code_action/handlers/remove_empty_port_connections.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/reformat_number_literal.rs	New assist: add/remove digit separators in integer literals.
crates/ide/src/code_action/handlers/pull_assignment_up.rs	New assists: pull assignment up/down (if/else ↔ ternary).
crates/ide/src/code_action/handlers/merge_nested_if.rs	New assist: merge nested if chains without else branches.
crates/ide/src/code_action/handlers/invert_if_else.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/insert_expected_token.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/extract_variable.rs	New assist: extract a selected expression into a new variable/net declaration.
crates/ide/src/code_action/handlers/expand_postfix_inc_dec.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/expand_compound_assignment.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/convert_port_declarations.rs	New assist: convert ANSI ↔ non-ANSI port declarations.
crates/ide/src/code_action/handlers/convert_ordered_connections.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/convert_named_port_connections.rs	New assist: expand/collapse named port shorthand connections.
crates/ide/src/code_action/handlers/convert_literal_base.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/convert_always_block.rs	New assist: convert between always, always_comb, and always_ff when safe.
crates/ide/src/code_action/handlers/apply_de_morgan.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/add_missing_parameters.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/add_missing_connections.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/add_instance_parens.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/add_implicit_named_port_parens.rs	Add assist documentation comments.
crates/ide/src/code_action/handlers/add_default_case_item.rs	Add assist documentation comments.
crates/hir/src/hir_def/subroutine.rs	Switch to lower_ident_opt in name lowering paths.
crates/hir/src/hir_def/expr/data_ty.rs	Fix default signing inference for vector types (avoid default-signed vectors).
crates/hir/src/hir_def/aggregate.rs	Extend StructSrc with typedef-name pointer and implement IsNamedSrc for it.
crates/hir/src/display.rs	Improve type-display formatting for signing/dimensions (ordering/spacing).

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