refactor(lib): stop exporting 23 symbols that never leave their module

[PathGao]

This fixes no bug. Nothing here changes behaviour, output, or performance. 23 declarations lose the export keyword and keep everything else. The benefit is that a reader opening one of these modules sees an interface that reflects what the module actually promises, instead of one where two thirds of the surface is noise.

npm test 565/565 (unchanged from 6b58cd5), npm run check 637 files / 0 errors, npm run build clean. No Rust touched.

The starting list was right about references and wrong about what follows

The candidates came from a scan for exported symbols in src/lib/**/*.ts with no consumer outside their defining file — 49 of them, after setting aside 29 that only scripts/ consumes. Re-checked here across src/, scripts/, src-tauri/, and the root config files: all 49 do have zero external references. That part held.

What did not hold is the conclusion. The scan excluded the defining file from its own search, so "no external reference" was being read as "dead". Printing every in-file occurrence of all 49 settles it:

Every one of the 49 is used inside its own file. Not one is an orphan. So the delete bucket is empty, and the whole question is export-removal versus keep.

classification	count
used inside its own file → export removed, declaration kept	23
used nowhere at all → declaration deleted	0
kept exported, with reason	26

The line

A type keeps export when it is directly the parameter type or the return type of an exported function, or the declared type of an exported constant. That is the module's stated interface: a caller who builds the argument in a separate statement (const ctx: PdfExportContext = {…}) or holds the result in a typed field has to be able to name it, and no importer existing yet is not evidence that none should.

A type loses export when it is only reachable inside such a type — a field of an options bag — or appears only in value positions internal to the module. Structural typing and inference cover those; a caller never has to write the name. A function loses export when every call to it is in its own file.

That rule decides all 49 without a tie-break, and re-exporting any of them later is a one-word change.

export removed (23)

symbol	file	why it is internal
SUPPORTED_LANGUAGES	stores/settings.svelte.ts	value position only — feeds SUPPORTED_LANGUAGE_CODES
SUPPORTED_LANGUAGE_CODES	stores/settings.svelte.ts	value position only — feeds isSupportedLanguage
isSupportedLanguage	stores/settings.svelte.ts	one call, :751, validating the persisted language key
loadPersistedSettings	stores/settings.svelte.ts	two calls, both in this file (:343, :423)
installPersistedSettings	stores/settings.svelte.ts	one call, :435
UpdatePhase	stores/update.svelte.ts	type of a field on a non-exported class; UpdateDialog.svelte compares updateStore.phase to string literals and never names the type
ErrorSource	stores/update.svelte.ts	same
EditorToolbarGroup	utils/editorToolbar.ts	field of EditorToolbarTool
EDITOR_TOOLBAR_TOOLS	utils/editorToolbar.ts	value position only — callers go through getEditorToolbarTools() and DEFAULT_EDITOR_TOOLBAR_ORDER
KatexFamilyRule	utils/exportFonts.ts	return type of parseKatexFamilyRules, which is itself internal
parseKatexFamilyRules	utils/exportFonts.ts	one call, :109, inside collectUsedKatexFamilies
collectClassNames	utils/exportFonts.ts	one call, :106, same
bytesToBase64	utils/exportFonts.ts	one call, :247, inside fetchFontDataUrls
FrontMatterValueKind	utils/frontMatter.ts	field of FrontMatterField
parseFrontMatterTagInput	utils/frontMatter.ts	two calls, both in this file
isAbsoluteMarkdownPath	utils/markdownLinks.ts	one call, :54
MermaidRenderer	utils/mermaidPrint.ts	field of PrintDiagramContext (which stays exported)
OpenExportedFileLabels	utils/openExportedFile.ts	optional field of OpenExportedFileDeps (which stays exported)
PASTE_PROBE_CHARACTER	utils/pasteContext.ts	value position only, :122
PasteContextTokenizer	utils/pasteContext.ts	field of PasteCaretContext (which stays exported)
isCodeAtOffset	utils/pasteContext.ts	one call, :156
TabFileActionId	utils/tabFileActions.ts	field of TabFileAction (which stays exported)
TITLEBAR_TOOLBAR_ACTIONS	utils/titlebarToolbar.ts	value position only — callers go through getTitlebarToolbarActions() and the two DEFAULT_TITLEBAR_TOOLBAR_* constants

Kept exported (26)

24 of them are the vocabulary of a module's public interface — the shape a caller has to name to build an argument or hold a result:

symbol	the exported signature it appears in
ExternalChangeOutcome	return of resolveExternalChange, which createDocumentSession hands back (documentSession.svelte.ts:630)
PersistedSetting	param of two helpers and return of createSettingsPersistence()
EditorToolbarMove	param of applyEditorToolbarMove, return of getEditorToolbar{Reorder,Adjacent}Move
ExportHtmlResult	return of exportAsHtml
PdfExportContext	param of exportAsPdf
ExportDocumentInput	param of buildExportDocument
KatexFontFace	return of findKatexFontFaces
PrintDiagramContext	param of renderDiagramsForPrint
ExportedFileFormat	param of askToOpenExportedFile
OpenExportedFileResult	return of askToOpenExportedFile
OpenExportedFileDeps	param of askToOpenExportedFile
PasteCaretContext	param of shouldLinkifyPastedUrl
PathIdentity	params of isSameFilePath
LineRange	return of parseSourceposLineRange
AnchorNode	param of findAnchorElement
AnchorMatch	return of findAnchorElement
RenderRichContentOptions	param of renderRichContent
TabFileAction	return of getTabFileActions
FileHistoryState	params and returns across six exported functions
FileHistoryNavigationState	params of replaceCurrentHistoryEntry, navigateFileHistory
FileHistoryNavigationResult	return of goBackInHistory, goForwardInHistory
TitlebarToolbarAction	return of getTitlebarToolbarActions
TitlebarToolbarMove	param of applyTitlebarToolbarMove, return of getTitlebarToolbar{Reorder,Adjacent}Move
ConfiguredTitlebarToolbarIds	return of getConfiguredTitlebarToolbarIds
DefaultFonts	declared type of the exported DEFAULT_FONTS, which Settings.svelte reads

PersistedSetting is the clearest of these. scripts/settingsPersistence.test.ts:100 needs that type and cannot import it, so it writes ReturnType<typeof createSettingsPersistence>[number] instead. The export is doing work even with no import naming it.

The 26th is TOC_WIDTH_RANGE, kept for a different reason — see below.

Two things found while classifying

settings.svelte.ts carries a second, stale copy of the language catalogue. The group of 8 the scan flagged in that file is not one feature's leftovers; it is two unrelated things, and only the language half is interesting. SUPPORTED_LANGUAGES (:55) duplicates getSupportedLanguages() in utils/i18n.ts:33 — same 26 entries, same code/name/nativeName shape — and settings.svelte.ts:27 duplicates i18n.ts:1's LanguageCode union. The live one is i18n.ts: Settings.svelte:1166-1168 renders the language <select> from it.

The two copies have already drifted. For pt, i18n.ts says Portuguese / Português; settings.svelte.ts says Portuguese (European) / Português (Europeu). Nothing catches that, because the settings copy is only consumed for its code column — .map((entry) => entry.code) on the next line. Its name and nativeName are never read by anything.

So the chain is live but only one column deep: SUPPORTED_LANGUAGES → SUPPORTED_LANGUAGE_CODES → isSupportedLanguage → validating the persisted language key at :751. Un-exporting is correct and is all this PR does. Deleting the duplicate — or deriving the codes from i18n.ts — is a real change with a real reason and belongs in its own PR.

TOC_WIDTH_RANGE is unreferenced because its consumer re-typed the numbers. It is one of five sibling NumericSettingRange constants; the other four are imported and consumed by Settings.svelte. NumericSettingRange's own doc comment (settings.svelte.ts:262-266) states the contract: "Single source of truth: the settings UI renders min/max/step from it and every write path clamps against the same object."

The TOC width control is the drag handle in MarkdownViewer.svelte, not a settings slider, and it does not import the range. It declares its own:

const TOC_MIN_WIDTH = 180;   // MarkdownViewer.svelte:267
const TOC_MAX_WIDTH = 420;   // MarkdownViewer.svelte:268

Identical to TOC_WIDTH_RANGE's min/max (:209), and used for the clamp at :430, the keyboard jumps at :444/:447, and aria-valuemin/aria-valuemax at :3468/:3469. The store's own setTocWidth clamps against TOC_WIDTH_RANGE as well, so the numbers agree today by coincidence of them being typed twice.

TOC_WIDTH_RANGE therefore keeps its export. Its unreferenced-ness is a defect in the caller, not surplus surface, and un-exporting it would cement the duplication and make the obvious fix start by re-adding the keyword. Not fixed here — importing the range into MarkdownViewer.svelte changes what a wrong number would do, which is more than a visibility PR should carry.

Not done

• No lint rule or test guards against the surface growing back. Nothing stops the next export with no importer. A scripts/ check in the shape of singleImplementationConvention.test.ts could assert it, but that is a source-text assertion with its own design questions and does not belong in the same change as the removals it would police.
• The 29 symbols referenced only from scripts/ are untouched, as intended. Removing export there would delete executable tests, which is the wrong trade in this repo.
• .svelte files were not scanned for their own unreferenced exports — only src/lib/**/*.ts was in scope.
• SUPPORTED_LANGUAGES's unread name/nativeName columns are left in place. Deleting data from a declaration is a different action from narrowing its visibility, and the whole constant is a duplicate that wants resolving as one decision.
• Verification is the compiler, not a behaviour run. npm run check covers src/ and scripts/ (637 files, 0 errors) and would name any broken reference; npm test is unchanged at 565 because none of these 23 were reachable from a test. The app was not launched — for a change that only removes a keyword from a declaration, there is nothing at runtime for it to observe.

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