agent-context-graph: doctor's skills-graph/actions-graph connector checks ignore resolved Memgraph config

[antejavor]

Summary

cli.py's _check_connector resolves the configured Memgraph connection (~/.config/context-graph/config.toml via resolve_memgraph_env()) for the sessions-graph connector check, but not for skills-graph or actions-graph — those two just call SkillGraph()/ActionsGraph() with no arguments, which fall back to Memgraph()'s own defaults (MEMGRAPH_URL env var, or bolt://localhost:7687) instead of whatever's actually configured.

Practical effect: agent-context-graph doctor --connector skills-graph (or actions-graph) reports FAIL connector:skills-graph: ValueError: Could not connect to Memgraph database...bolt://localhost:7687 even when the configured instance (a different URL) is reachable and correctly set up -- runtime:<name>'s own smoke check fails the same way, for the same reason, since it also builds its AgentLink without passing the resolved config through.

Repro

With ~/.config/context-graph/config.toml pointing at a non-default Memgraph URL (e.g. a remote/HA instance, or just a different local port) that is reachable and has the connector's schema set up:

agent-context-graph doctor --runtime codex --connector skills-graph
# OK memgraph: <configured-url> reachable
# FAIL connector:skills-graph: ValueError: Could not connect to Memgraph database. Please ensure the URL 'bolt://localhost:7687' is correct
# FAIL runtime:codex: ValueError: Could not connect to Memgraph database. Please ensure the URL 'bolt://localhost:7687' is correct

Confirmed this is pre-existing (reproduces identically on main before any of the recent context-graph work) -- not a regression from #271/#273.

Where

• context-graph/agent-context-graph/src/agent_context_graph/cli.py's _check_connector -- the sessions_graph branch does resolve_memgraph_env() + passes url/username/password/database explicitly; the skills_graph and actions_graph branches don't.
• Same root cause likely affects _check_runtime, which calls create_link(connectors) (via hooks/runner.py post-agent-context-graph: entry_points-based runtime plugin registry #273) with no memgraph_env argument at all.

Fix sketch (not yet designed/confirmed)

Resolve memgraph_env once in _doctor() and thread it through to every _check_connector call and into _check_runtime, matching what sessions_graph's branch and _check_memgraph() already do.