fix(drill): lay the harness's kit down before boot instead of reloading Kits (#22)

Run 48 deleted Kits' file for a fresh start, and the harness's
rnhrevolver kit, added after boot with `oxide.reload Kits` through the
panel's command endpoint, never reached Kits: no reload or compile job
followed, and every test profile was refused for want of the kit.

The drill now replaces kits_data.json with one holding only that kit.
Kits reads it at boot; RunicNPC's first load adds its example kits
beside it (it skips kits already there) and settles its own Kits
reload (D329). The add-after-boot stays as a fallback, now through the
console's websocket, and is a finding when Kits does not load again.

Refs #20, #22

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

README.md

@@ -153,8 +153,9 @@ the week. A run by hand always goes ahead.
   plugin against them.
 - **Live, once per build** (`tools/drill/drill.js live`): the `rust-staging` server (Oxide, a 3500 map)
   installs the same pair at start (`tools/drill/rig-start.sh`), loads RunicNPC, Kits and
-  `tools/RunicNpcTest.cs`, and runs `rnt.run all`. It starts the server from empty Kits and RunicNPC data
-  (their files are deleted first, so the example kits are written afresh) and gives up on the harness after
+  `tools/RunicNpcTest.cs`, and runs `rnt.run all`. It starts the server from fresh Kits and RunicNPC data
+  (RunicNPC's files are deleted and Kits' file holds only the harness's kit, so the example kits are written
+  afresh) and gives up on the harness after
   5 minutes with no new output (45 minutes at most), putting the tail of the server's log in the issue. When
   both 6000-map rigs are running, `rust-carbon` is stopped for it and started again.
 - **Report:** anything that fails or differs opens one issue for that build, labelled `staging-drill`.