Add AgentAd ad schemas as a LogicSRC primitive

AgentAd is a disclosed, agent-readable advertising contract for CLI tools
and AI agents. LogicSRC owns the canonical schemas; cl1s.tech is the
reference network built on them.

- packages/schemas: agentad-{ad,placement,ad-request,ad-response,
  impression,click,campaign} schemas (id under schemas.logicsrc.com) +
  ad/placement fixtures, exported from @logicsrc/schemas
- packages/validators: register the 7 agentad kinds, wire fixture
  validation, add tests (disclosure.sponsored must be true)
- docs/agentad.md: the AgentAd spec
- README: list AgentAd under v1 priorities

Validators build clean; all fixtures validate; vitest 4/4 green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/validators/src/cli.ts

@@ -7,7 +7,7 @@ function main(argv: string[]) {
   const [, , kindArg, fileArg] = argv;
 
   if (!kindArg || !fileArg) {
-    console.error("Usage: logicsrc-validate <task|agent|run|event|plugin> <file.yaml|file.json>");
+    console.error("Usage: logicsrc-validate <task|agent|run|event|plugin|agentad-ad|agentad-placement|...> <file.yaml|file.json>");
     process.exitCode = 2;
     return;
   }