MCP `drills`: each failure domain, its last drill and verdict, and the command that runs it, for a forge admin

For: the drills a person must run (see #5367 and #5368) are one question away in any harness. This is the lower half of /settings/backups.

Done:

[ ] A read-only tool drills answers one row per failure domain from listResilience (src/actions/resilience.ts): key, what breaks, the last drill's time, green or red and why, or the sentence on why it is not drilled. Each drillable domain also gets its exact command from drillCommand (src/kernel/domain_drill.ts). Admin only, refused in the page's words.
[ ] test/mcp-drills.test.ts covers two cases: an admin sees every domain, with a command for each drillable one; a non-admin is refused. Each fails without the tool.
[ ] One row in docs/MCP.md.
[ ] Before pushing, run the new test, test/mcp.test.ts, test/mcp-docs.test.ts and test/mcp-size.test.ts. A red test elsewhere that main also has is named in the pull, not a reason to stop.

Risk: test/mcp-size.test.ts caps tools/list. Keep the description to one short sentence and the tool to no arguments.

MCP `drills`: each failure domain, its last drill and verdict, and the command that runs it, for a forge admin #5416