feat: complete SKILL.md standard implementation - replace instruments

This commit completes the replacement of Agent Zero's legacy "instruments"
system with the open SKILL.md standard (originally developed by Anthropic).

- Remove INSTRUMENTS from Memory.Area enum, keep only SKILLS
- Update memory.py to load skills instead of instruments
- Update memory_consolidation.py docstrings

- Delete agent.system.instruments.md (deprecated)
- Update solving.md: "prefer skills" instead of "prefer instruments"
- Update tips.md: Skills section with SKILL.md standard reference
- Update tool.skills.md: Cross-platform compatibility note

- architecture.md: Full rewrite of Skills section with SKILL.md format
- installation.md: Update directory structure references
- extensibility.md: Update component terminology
- README.md: Update navigation links

- Update memory dashboard filter options (instruments → skills)
- Update area color mappings

- .gitignore: Update skill patterns (builtin instead of default)
- .dockerignore: Same patterns
- backup.py: Update backup include patterns

- Cross-platform: Works with Claude Code, Cursor, Goose, Codex CLI
- YAML frontmatter for structured metadata
- Semantic recall from vector memory
- Token efficient (not in system prompt)

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -33,12 +33,12 @@ knowledge/**
 !knowledge/default/
 !knowledge/default/**
 
-# Handle instruments directory
-instruments/**
-!instruments/**/
-# Explicitly allow the default folder in instruments
-!instruments/default/
-!instruments/default/**
+# Handle skills directory (SKILL.md standard)
+skills/**
+!skills/**/
+# Explicitly allow the builtin folder in skills
+!skills/builtin/
+!skills/builtin/**
 
 # Global rule to include .gitkeep files anywhere
 !**/.gitkeep