feat(messaging): add inbox, conversation, search, and send tools

[5queezer]

Summary

Adds 4 new messaging tools to the LinkedIn MCP server (#234):

• get_inbox — list recent conversations from messaging inbox
• get_conversation — read a specific thread by username or thread_id
• search_conversations — search messages by keyword
• send_message — send a message to a LinkedIn user

Checklist

Code

• Add extractor methods to LinkedInExtractor (scraping/extractor.py)
• Add messaging.py tool registration (tools/messaging.py)
• Register tools in create_mcp_server() (server.py)
• Add "messaging" reference kind (scraping/link_metadata.py)

Tests

• Add mock methods to _make_mock_extractor (tests/test_tools.py)
• Add TestMessagingTools class (tests/test_tools.py)
• Add TestMessaging class (tests/test_scraping.py)
• Add messaging URL classification tests (tests/test_link_metadata.py)
• Update TestToolTimeouts.tool_names tuple

Docs

• Update tool table in README.md
• Update features list in docs/docker-hub.md
• Add tools to manifest.json

Verify

• uv run pytest --cov — 297 passed, 74.32% coverage
• uv run ruff check . && uv run ruff format .
• uv run ty check
• uv run pre-commit run --all-files
• Live test get_inbox
• Live test get_conversation
• Live test search_conversations
• Live test send_message

Test plan

• Start server: uv run -m linkedin_mcp_server --transport streamable-http --log-level DEBUG
• Verify get_inbox returns conversation list
• Verify get_conversation with a known username returns messages
• Verify search_conversations returns filtered results
• Verify send_message sends to a test account (⚠️ destructive — first write tool)

Notes

• send_message is the first write operation in the server. It uses readOnlyHint: false and openWorldHint: true to signal MCP clients to confirm before sending.
• Messaging tools don't follow the section-config pattern in fields.py — each method navigates directly.
• LinkedIn may restrict messaging to 1st-degree connections. The tool handles "Message" button absence with a clear error.

Generated with Claude Opus 4.6. Prompt: Implement the following plan: LinkedIn Messaging Tools

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