chore: convert the knip config to jsonc with rationale comments

Review asked for inline explanations of the @openai/codex exclusion and
the warn-level rule strategy; plain JSON cannot carry comments, so the
config becomes knip.jsonc (a format knip resolves natively) with both
rationales documented in place.

https://claude.ai/code/session_01XNtnkLbBiXZxfQQYLMpucB

Author: claude

knip.json knip.jsoncknip.json renamed to knip.jsonc

@@ -29,9 +29,17 @@
 		"where"
 	],
 	"ignoreDependencies": [
+		// Editor-only LSP tooling; never imported.
 		"typescript-language-server",
+		// The official Codex CLI this package wraps: resolved from the HOST
+		// install at runtime (scripts/codex-bin-resolver.js), deliberately not
+		// a package.json dependency.
 		"@openai/codex"
 	],
+	// Export/type-level findings are warn-only on purpose: the blocking signal
+	// is unused FILES and DEPENDENCIES. The export backlog was cleared
+	// incrementally (PRs #556/#557, down to two documented keepers); escalate a
+	// rule to "error" once its warning count is intentionally pinned at zero.
 	"rules": {
 		"exports": "warn",
 		"types": "warn",