feat(agent): add algorithmic problem-solving patterns (fluent_cli-o6k)

Add AlgorithmPatternDetector with 10 built-in algorithm patterns for
intelligent task reasoning:
- BFS/DFS for search problems
- A* and Dijkstra for pathfinding
- Dynamic programming detection
- Sliding puzzle recognition
- Backtracking patterns
- Union-Find for connected components
- Greedy algorithms
- Binary search patterns

Each pattern includes:
- Keyword matching for detection
- Characteristic identification
- Step-by-step guidance
- Common pitfalls to avoid
- Time/space complexity info
- Example code snippets

Adds prompt augmentation to inject algorithm-specific guidance into
agent reasoning when algorithmic tasks are detected.

Includes 7 unit tests covering pattern detection and prompt generation.

Author: njfio