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/errors.ts

@@ -0,0 +1,88 @@
+/**
+ * Transaction System Errors
+ *
+ * Provides detailed error information for transaction failures.
+ */
+
+/**
+ * Base class for all transaction errors
+ */
+export class TransactionError extends Error {
+  constructor(
+    message: string,
+    public readonly context?: Record<string, any>
+  ) {
+    super(message)
+    this.name = 'TransactionError'
+    Error.captureStackTrace(this, this.constructor)
+  }
+}
+
+/**
+ * Error during transaction execution
+ */
+export class TransactionExecutionError extends TransactionError {
+  constructor(
+    message: string,
+    public readonly operationIndex: number,
+    public readonly operationName: string | undefined,
+    public readonly cause: Error
+  ) {
+    super(message, {
+      operationIndex,
+      operationName,
+      cause: cause.message
+    })
+    this.name = 'TransactionExecutionError'
+  }
+}
+
+/**
+ * Error during transaction rollback
+ */
+export class TransactionRollbackError extends TransactionError {
+  constructor(
+    message: string,
+    public readonly originalError: Error,
+    public readonly rollbackErrors: Error[]
+  ) {
+    super(message, {
+      originalError: originalError.message,
+      rollbackErrorCount: rollbackErrors.length,
+      rollbackErrors: rollbackErrors.map(e => e.message)
+    })
+    this.name = 'TransactionRollbackError'
+  }
+}
+
+/**
+ * Error for invalid transaction state
+ */
+export class InvalidTransactionStateError extends TransactionError {
+  constructor(
+    currentState: string,
+    attemptedAction: string
+  ) {
+    super(
+      `Cannot ${attemptedAction}: transaction is in state '${currentState}'`,
+      { currentState, attemptedAction }
+    )
+    this.name = 'InvalidTransactionStateError'
+  }
+}
+
+/**
+ * Error for transaction timeout
+ */
+export class TransactionTimeoutError extends TransactionError {
+  constructor(
+    timeoutMs: number,
+    operationIndex: number
+  ) {
+    super(
+      `Transaction timed out after ${timeoutMs}ms at operation ${operationIndex}`,
+      { timeoutMs, operationIndex }
+    )
+    this.name = 'TransactionTimeoutError'
+  }
+}