Replace the connector-coupled BUILTIN_TOOLS registry with a pure-data
catalog so shared/tools no longer imports any connector module, making the
connector packages independently deletable.
- add shared/tools/catalog.py (ToolMetadata + TOOL_CATALOG, 41 tools, no imports)
- point GET /agent/tools (the only live consumer) at the catalog
- relocate ToolDefinition into action_log middleware (its sole consumer);
drop the inert tool_definitions wiring (no tool defines reverse)
- delete shared/tools/registry.py: connector imports, dead factories,
dead get_connector_gated_tools, and BUILTIN_TOOLS
- drop stale dedup-propagation test (path removed in C1) + refresh docstrings
import-all guardrail + agents unit suite green (987 passed).