fix: align continuity_context output schema - #32

Problem

The public structured-output schema classified constraints as an array even though bounded continuity contexts return an object. Standards-compliant modern MCP clients therefore rejected successful calls, and actor-memory-specific output fields were left unspecified.

Solution

• describe ordinary, actor-memory, and bounded continuity response fields in one Draft 2020-12 schema
• make constraints and delegation contracts exact and bounded
• keep actor memory aligned with the published v1 context contract
• reject undeclared top-level continuity output fields
• exercise all three response shapes through a real MCP 2026-07-28 client

Verification

• uv run --package sagasmith-coc-mcp pytest packages/mcp/tests/test_collection_pagination_contract.py packages/mcp/tests/test_tool_contract_quality.py (16 passed)
• uv run --package sagasmith-coc-mcp pytest packages/mcp/tests (90 passed)
• uv run ruff check packages/mcp/src packages/mcp/tests

Closes #31