Reject streaming agent methods from MCP export

[vigoo]

Overview

• reject stream-bearing agent methods from MCP capability and prompt export
• expose parameterless methods as resources or resource templates only when they are read-only; export other non-streaming methods as tools
• add unit and end-to-end MCP listing coverage, including auto-injected parameters and recursive stream schemas

This is aligned with #3789 and does not add an MCP protocol extension or buffer streams into arrays.

Verification

• cargo test -p golem-worker-service --lib -- agent_mcp_capability::tests --report-time
• cargo clippy -p golem-worker-service --lib --tests -- -D warnings
• cargo check -p golem-worker-service --all-targets
• cargo clippy -p integration-tests --test integration --no-deps -- -D warnings
• SQLite MCP integration tests for listing tools, resources, resource templates, and prompts
• rebuilt the agent-mcp test component
• package-scoped formatting and git diff --check

Resolves GOL-94

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