refactor(8.0): delete DataAPI — superseded by Db persist/restore + import API + stats

The legacy backup/import/export/stats facade (src/api/DataAPI.ts) drifted
from the modern entity shape and every job it did now has a first-class
surface. Delete it and brain.data(), and rewire the CLI:

- data-stats → brain.stats() (full BrainyStats report: per-type breakdowns,
  indexed fields, index health, storage backend, writer lock, version)
- clean → brain.clear()
- export → alias of snapshot; a db.persist() snapshot is the full-fidelity
  export format (open with Brainy.load, load wholesale with brainy restore);
  external data ingestion remains brainy import (UniversalImportAPI)

Rewiring clean onto brain.clear() exposed two real bugs, both fixed:

- clear() left this.graphIndex undefined forever — any graph-touching call
  afterwards (relate, getNeighbors, stats) crashed. clear() now re-resolves
  the graph index exactly as init() does and re-wires the shared UUID↔int
  resolver, and re-resolves the metadata index with the same provider
  fallback as init().
- storage.clear() reset the legacy totals but not the per-type/subtype
  count rollups or id→type caches, so stats() reported phantom counts for
  deleted entities. Both adapters now delegate derived-state reset to
  reloadDerivedState(), the same path restore-from-snapshot uses.

One-shot CLI commands (data-stats, clean, snapshot/export, restore,
history, generation) now close the brain and exit explicitly — global
cache timers otherwise keep the process alive holding the writer lock.

Verified: build clean, 1383/1383 unit tests, 24/24 db-mvcc integration,
plus an end-to-end CLI smoke (add → data-stats → export → clean →
data-stats).

src/cli/commands/core.ts

@@ -1,13 +1,14 @@
 /**
- * Core CLI Commands - TypeScript Implementation
- * 
- * Essential database operations: add, search, get, relate, import, export
+ * @module cli/commands/core
+ * @description Essential database CLI commands: add, search, get, update,
+ * delete, relate, unrelate, and diagnostics. Database export lives under
+ * `brainy snapshot` (aliased as `brainy export`) — a `db.persist()` snapshot
+ * is the full-fidelity export format.
  */
 
 import chalk from 'chalk'
 import ora from 'ora'
 import inquirer from 'inquirer'
-import { readFileSync, writeFileSync } from 'node:fs'
 import { Brainy } from '../../brainy.js'
 import { BrainyTypes, NounType, VerbType } from '../../index.js'
 
@@ -66,10 +67,6 @@ interface RelateOptions extends CoreOptions {
   subtype?: string
 }
 
-interface ExportOptions extends CoreOptions {
-  format?: 'json' | 'csv' | 'jsonl'
-}
-
 let brainyInstance: Brainy | null = null
 
 const getBrainy = (): Brainy => {
@@ -866,82 +863,6 @@ export const coreCommands = {
     }
   },
 
-  /**
-   * Export database
-   */
-  async export(file: string | undefined, options: ExportOptions) {
-    const spinner = ora('Exporting database...').start()
-    
-    try {
-      const brain = getBrainy()
-      const format = options.format || 'json'
-      
-      // Export all data
-      const dataApi = await brain.data()
-      const data = await dataApi.export({ format: 'json' })
-      let output = ''
-      
-      switch (format) {
-        case 'json':
-          output = options.pretty 
-            ? JSON.stringify(data, null, 2)
-            : JSON.stringify(data)
-          break
-          
-        case 'jsonl':
-          if (Array.isArray(data)) {
-            output = data.map(item => JSON.stringify(item)).join('\n')
-          } else {
-            output = JSON.stringify(data)
-          }
-          break
-          
-        case 'csv':
-          if (Array.isArray(data) && data.length > 0) {
-            // Get all unique keys for headers
-            const headers = new Set<string>()
-            data.forEach(item => {
-              Object.keys(item).forEach(key => headers.add(key))
-            })
-            const headerArray = Array.from(headers)
-            
-            // Create CSV
-            output = headerArray.join(',') + '\n'
-            output += data.map(item => {
-              return headerArray.map(h => {
-                const value = item[h]
-                if (typeof value === 'object') {
-                  return JSON.stringify(value)
-                }
-                return value || ''
-              }).join(',')
-            }).join('\n')
-          }
-          break
-      }
-      
-      if (file) {
-        writeFileSync(file, output)
-        spinner.succeed(`Exported to ${file}`)
-        
-        if (!options.json) {
-          console.log(chalk.green(`✓ Successfully exported database to ${file}`))
-          console.log(chalk.dim(`  Format: ${format}`))
-          console.log(chalk.dim(`  Items: ${Array.isArray(data) ? data.length : 1}`))
-        } else {
-          formatOutput({ file, format, count: Array.isArray(data) ? data.length : 1 }, options)
-        }
-      } else {
-        spinner.succeed('Export complete')
-        console.log(output)
-      }
-    } catch (error: any) {
-      spinner.fail('Export failed')
-      console.error(chalk.red(error.message))
-      process.exit(1)
-    }
-  },
-
   /**
    * Show plugin and provider diagnostics
    */