chore(ci): ratchet dead-code baseline 79 → 78 after main merge (#282)

Merging main (#505 CLI dedupe) removed a dead symbol, dropping knip's
count to 78. Lock in the gain so the ratchet holds at the lower number.

Author: bgagent

knip-baseline.json

@@ -1,4 +1,4 @@
 {
-  "count": 79,
+  "count": 78,
   "comment": "Dead-code ratchet baseline for issue #282 (cairn MVG gate #6). This is the knip issue count at the time the gate was introduced — pre-existing unused exports/types that are out of scope to remove in the gate PR. The ratchet (scripts/check-deadcode-ratchet.mjs) fails the build only if the count rises above this number. When dead code is removed and the count drops, lower this value in the same PR to lock in the gain. Per-category false positives belong in knip.json, not here."
 }