feat: add v5.8.0 features - transactions, pagination, and comprehensive docs

**Transaction System (TIER 1.2)**
- Atomic operations with automatic rollback
- 36 unit tests + 35 integration tests passing
- Full documentation in docs/transactions.md

**Duplicate Check Optimization (TIER 1.4)**
- Optimized from O(n) to O(log n) using GraphAdjacencyIndex
- Uses LSM-tree for efficient lookups
- Tests verify performance improvements

**GraphIndex Pagination (TIER 1.5)**
- Production-scale pagination for high-degree nodes
- Backward compatible API
- 18 pagination tests passing

**Comprehensive Filter Documentation (TIER 1.6)**
- Complete operator reference (15 operators)
- Compound filters (anyOf, allOf, nested logic)
- Common query patterns and troubleshooting guide
- 642 lines of new documentation

**README Updates**
- Added Filter & Query Syntax Guide to Essential Reading
- Added Transactions to Core Concepts section

All changes tested and production-ready for v5.8.0 release.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/transaction/types.ts

@@ -0,0 +1,103 @@
+/**
+ * Transaction System Types
+ *
+ * Provides atomicity for Brainy operations - all succeed or all rollback.
+ * Prevents partial failures that leave system in inconsistent state.
+ */
+
+/**
+ * Transaction state
+ */
+export type TransactionState =
+  | 'pending'      // Created but not executed
+  | 'executing'    // Currently executing operations
+  | 'committed'    // Successfully committed
+  | 'rolling_back' // Rolling back due to failure
+  | 'rolled_back'  // Successfully rolled back
+
+/**
+ * Rollback action - undoes an operation
+ * Must be idempotent (safe to call multiple times)
+ */
+export type RollbackAction = () => Promise<void>
+
+/**
+ * Operation that can be executed and rolled back
+ */
+export interface Operation {
+  /**
+   * Execute the operation
+   * @returns Rollback action to undo this operation (or undefined if no rollback needed)
+   */
+  execute(): Promise<RollbackAction | undefined>
+
+  /**
+   * Optional: Name of operation for debugging
+   */
+  readonly name?: string
+}
+
+/**
+ * Transaction context passed to user functions
+ */
+export interface TransactionContext {
+  /**
+   * Add an operation to the transaction
+   */
+  addOperation(operation: Operation): void
+
+  /**
+   * Get current transaction state
+   */
+  getState(): TransactionState
+
+  /**
+   * Get number of operations in transaction
+   */
+  getOperationCount(): number
+}
+
+/**
+ * Function that builds a transaction
+ */
+export type TransactionFunction<T> = (ctx: TransactionContext) => Promise<T>
+
+/**
+ * Transaction execution result
+ */
+export interface TransactionResult<T> {
+  /**
+   * Result value from user function
+   */
+  value: T
+
+  /**
+   * Number of operations executed
+   */
+  operationCount: number
+
+  /**
+   * Execution time in milliseconds
+   */
+  executionTimeMs: number
+}
+
+/**
+ * Transaction execution options
+ */
+export interface TransactionOptions {
+  /**
+   * Timeout in milliseconds (default: 30000 = 30 seconds)
+   */
+  timeout?: number
+
+  /**
+   * Whether to log transaction execution (default: false)
+   */
+  logging?: boolean
+
+  /**
+   * Maximum number of rollback retry attempts (default: 3)
+   */
+  maxRollbackRetries?: number
+}