refactor: change AST to CST

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[Copilot]

Pull request overview

This PR renames the project’s internal syntax tree terminology from AST to CST across the codebase, aligning file/module names, public/internal APIs, and documentation with “Concrete Syntax Tree” wording while keeping functionality largely the same.

Changes:

• Renamed core types/functions/parameters from AST → CST across parsing, traversal, patching, and serialization.
• Updated TomlDocument to store _cst and adjusted patch/update flows to use CST naming.
• Added a deprecated compatibility wrapper for TomlFormat.autoDetectFormatWithAst (now forwarding to autoDetectFormatWithCst).

Reviewed changes

Copilot reviewed 33 out of 33 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/writer.ts	Switched imports/docs from ./ast to ./cst and updated terminology in comments/JSDoc.
src/truncate.ts	Renamed truncate API to truncateCst and updated parameter/return naming to CST.
src/traverse.ts	Renamed traverse input from ast to cst and updated imports/docs accordingly.
src/toml-format.ts	Renamed format auto-detect helper to autoDetectFormatWithCst; added deprecated autoDetectFormatWithAst wrapper.
src/toml-document.ts	Internal storage renamed to _cst; patch/update/overwrite flows updated to CST naming; added CST/AST accessors.
src/to-toml.ts	Updated types/docs to accept CST and use CST naming throughout.
src/to-js.ts	Updated types/docs and iteration variable naming from AST to CST.
src/patch.ts	Renamed exported patch helper patchAst → patchCst and updated internal variables/docs to CST.
src/parse-toml.ts	Updated generator return type from AST to CST and renamed documentation to CST.
src/parse-js.ts	Updated imports/docs to CST terminology.
src/index.ts	Updated exported documentation comment to reference CST.
src/generate.ts	Updated module/file documentation and imports to CST.
src/formatter.ts	Updated imports to CST module.
src/find-by-path.ts	Updated imports and docs to reference CST structure/semantics.
src/cst.ts	Updated terminology to “Concrete Syntax Tree” and renamed exported tree type to CST.
src/comment-alignment.ts	Updated imports and docs to CST terminology.
src/tests/writer.test.ts	Updated imports and local variable naming (ast → cst).
src/tests/validate-cst.test.ts	Updated imports and patch helper usage to patchCst; updated CST wording.
src/tests/truncate.test.ts	Updated tests to use truncateCst and CST naming.
src/tests/toml-format.test.ts	Updated tests to use autoDetectFormatWithCst and CST variable names.
src/tests/toml-document.test.ts	Updated test descriptions and access to use doc.cst rather than doc.ast.
src/tests/to-toml.test.ts	Updated test description to CST wording.
src/tests/roundtrip.patch-parse.test.ts	Updated equality assertion to compare cst structures.
src/tests/patch.test.ts	Updated comments to CST wording.
src/tests/parse-toml.test.ts	Updated imports to CST module.
src/tests/parse-js.test.ts	Updated imports/types (AST → CST) and helper naming.
src/tests/generate.test.ts	Updated imports to CST module.
src/tests/find-by-path.test.ts	Updated imports and local variable names to CST.
src/tests/detect-trailing-comma.test.ts	Updated tests to pass CST variables into detection helpers.
src/tests/cst-parsing.test.ts	Updated suite naming/snapshots to CST wording and CST variable names.
src/tests/continue-parsing.test.ts	Updated test descriptions to CST wording.
src/tests/snapshots/cst-parsing.test.ts.snap	Snapshot keys updated from AST-focused names to CST-focused names.
README.md	Updated user-facing documentation to reference CST instead of AST.

Comments suppressed due to low confidence (1)

src/cst.ts:36

• The AST type alias was removed in favor of CST. If external code referenced the AST type name (even if the underlying structure is unchanged), this forces a breaking rename. Consider exporting type AST = CST as a /** @deprecated */ alias to smooth the transition.

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