Windows path fixes and agent system prompt enhancements

[hackerxj2010]

Summary

This PR fixes Windows compatibility issues across the test suite and enhances all sub-agent system prompts for more powerful, thorough code assistance.

Windows Path Fixes

• SDK tests: Fixed path normalization (backslash/drive-letter handling) in path-utils, code-search, read-files, initial-session-state, run-file-filter, and filesystem tests
• CLI tests: Fixed init-direnv tests (skip on Windows), path-completion separator, added Immer enableMapSet() for MessageBlockStore
• Mock utilities: Fixed createMockFs to normalize Windows paths correctly

Agent System Prompt Enhancements

• Base2 (Buffy): Better agent orchestration guidance, parallel spawning, thoroughness mandates
• Editor: SOLID principles, type safety enforcement, pre-reasoning step
• Thinker agents: Structured reasoning methodologies (Deconstruct/Analyze/Synthesize)
• Basher: Concrete command output analysis guidelines
• File-picker / Code-searcher / File-lister: Better guidance for thorough file discovery
• Researcher-web / Researcher-docs: Systematic information gathering methodology
• Code-reviewer: Deeper review methodology with edge-case analysis

Testing

All 2,741 combined tests pass (SDK + CLI), 0 failures, 30 skipped (all expected Windows-only skips).