feat: Add performance caching system

[anjor]

Feature Request: Performance Caching System

Overview

Implement intelligent caching to improve CLI performance by reducing redundant API calls and storing frequently accessed data locally.

Proposed Implementation

• Authentication Token Caching: Cache valid tokens to reduce auth overhead
• API Response Caching: Cache dataset metadata, ontology schemas, user/group info
• Query Result Caching: Optional caching for expensive SQL query results
• Smart Cache Invalidation: Time-based and content-based cache expiration
• Cache Management Commands: pltr cache clear, pltr cache status, pltr cache config

Cache Strategy

• Location: ~/.cache/pltr/ following XDG standards
• TTL Defaults:
  • Auth tokens: 30 minutes
  • API responses: 5 minutes
  • Query results: User configurable (default disabled)
• Size Limits: Configurable max cache size with LRU eviction
• Security: Sensitive data encryption at rest

Use Cases

• Repeated Commands: Faster execution of frequently run operations
• Interactive Shell: Improved responsiveness in pltr shell mode
• Development Workflows: Faster iteration when working with same datasets
• Large Result Sets: Optional caching of expensive query results

Technical Requirements

• Thread-safe cache implementation
• Configurable cache policies per command type
• Automatic cleanup of expired entries
• Optional cache bypass with --no-cache flag
• Cache statistics and monitoring

Acceptance Criteria

• Authentication tokens cached and reused within TTL
• API responses cached with smart invalidation
• Cache configuration via pltr configure cache
• Cache management commands functional
• Significant performance improvement measurable
• Security audit of cached sensitive data
• Comprehensive test coverage including cache behavior

Priority: Medium
Labels: enhancement, Phase-8
Effort: Medium