Replace outdated "marketplace" terminology with "packages" across documentation

[Copilot]

Documentation contained 75+ references to deprecated "marketplace" terminology. This has been superseded by "packages" in current codebase.

Changes

Core Documentation (7 files)

• src/uacs/__init__.py - Module docstring
• docs/features/ADAPTERS.md - Validation messages, cross-references
• docs/CLI_REFERENCE.md, docs/LIBRARY_GUIDE.md, docs/ARCHITECTURE.md - Terminology and examples
• CONTRIBUTING.md - Directory structure, test names
• pyproject.toml - Ruff config path

Integration Guides (4 files)

• docs/features/INTEGRATIONS.md - MCP tool names and descriptions
• docs/integrations/{CURSOR,WINDSURF,CLAUDE_DESKTOP}.md - Full terminology update

Historical Documents (2 files)

• CHANGELOG.md, .github/RELEASE_NOTES_v0.1.0.md - Consistency updates

Terminology Mapping

marketplace             → packages
marketplace integration → package management  
marketplace_search      → packages_search
marketplace_install     → packages_install
MARKETPLACE.md          → PACKAGES.md (links updated)

Verification

• All 112 documentation cross-references validated
• docs/MARKETPLACE.md retained as redirect with deprecation notice

Original prompt

Review each documentation file. Look for outdated references. Such as marketplace. This has been replaced with packages. The adapters doc for instance still says marketplace. So a full review and document each instance for future updating.

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