Fix arrow function and function expression export indexing

[GeneralClaw]

Problem

CodeGraph v0.3.1 fails to index three common TypeScript/JavaScript patterns:

1. Arrow function exports: export const useAuth = () => { ... } — the arrow_function AST node has no name field, so extractName() returns '<anonymous>' and bails.
2. Type aliases: export type AuthContextValue = { ... } — type_alias_declaration isn't in any extraction list.
3. Non-function variable exports: export const store = create(...), export const schema = z.object(...), export const config = { ... } — these are call_expression, object, or primitive values, not functions, so they're never visited.

Additionally, isExported() for TS/JS uses a 10-char substring lookback that misses export for deeply nested nodes.

Real-World Impact

Tested on a production monorepo (Expo + FastAPI, 238 files):

Metric	Before	After	Change
Nodes	779	1,172	+50%
Edges	2,599	3,489	+34%
packages/ nodes	0	166	Was completely invisible
variable nodes	0	109	New kind
type_alias nodes	0	105	New kind

7 shared packages (auth, db, cv, i18n, ui, analytics, config) had zero nodes. After this fix, all have full coverage. Only 4 files remain at 0 nodes — all are re-export barrels or ambient declarations with no extractable symbols.

Changes (2 commits)

Commit 1: Arrow function + isExported fix

extractFunction(): When arrow_function or function_expression resolves to '<anonymous>', check the parent variable_declarator for the name:

let name = extractName(node, this.source, this.extractor);
if (name === '<anonymous>' &&
    (node.type === 'arrow_function' || node.type === 'function_expression')) {
  const parent = node.parent;
  if (parent?.type === 'variable_declarator') {
    const varName = getChildByField(parent, 'name');
    if (varName) name = getNodeText(varName, this.source);
  }
}

isExported() (TS + JS): Walk the parent chain instead of 10-char lookback:

isExported: (node, _source) => {
  let current = node.parent;
  while (current) {
    if (current.type === 'export_statement') return true;
    current = current.parent;
  }
  return false;
},

Commit 2: Type alias + exported variable extraction

typeAliasTypes: New field on LanguageExtractor interface. Populated for TypeScript (type_alias_declaration), Go (type_spec), Rust (type_item), C (type_definition), C++ (type_definition, alias_declaration), Swift (typealias_declaration), Kotlin (type_alias). Empty for languages without type aliases.

extractTypeAlias(): New method that creates type_alias kind nodes.

extractExportedVariables(): New method called when visiting export_statement nodes. Finds lexical_declaration > variable_declarator children whose values are NOT already handled by functionTypes (avoids duplicating arrow functions). Creates variable kind nodes for:

• Zustand stores: export const useX = create(...)
• XState machines: export const xMachine = createMachine(...)
• Zod schemas: export const schema = z.object(...)
• Config objects: export const config = { ... }
• Constants: export const MAX = 3
• Arrays: export const NAMES = [...] as const

Tests

Added 17 new test cases in __tests__/extraction.test.ts:

Arrow function tests (6):

• Exported arrow functions, function expressions, non-exported, anonymous, multiple exports, JavaScript files

Type alias tests (3):

• Exported type aliases, non-exported, multiple in same file

Exported variable tests (8):

• Zustand stores, object literals, arrays, primitives, Zod schemas, XState machines
• No duplication with arrow functions
• Non-exported const not treated as exported

All 215 tests pass (59 extraction + 156 others). Zero regressions in evaluation benchmarks.

AST Context

For export const useAuth = () => { ... }, tree-sitter produces:

export_statement
  lexical_declaration
    variable_declarator
      name: identifier "useAuth"
      value: arrow_function

For export const config = { ... }:

export_statement
  lexical_declaration
    variable_declarator
      name: identifier "config"
      value: object

The arrow_function/object nodes are 3 levels deep under export_statement, which is why the 10-char lookback failed and why parent-chain walking is needed.