test(rules): mirror and cover AG2-018

[bradAGI]

Engine half of a coordinated pair. Rules half: trustabl/agent-reliability-rules#74, on a branch of the same name, so the rules-sync job resolves the matching pack rather than main. Neither half should merge alone — check-rules-sync.sh fails if they do.

What the pair adds

AutoGen had no observability rule; OpenAI ships OAI-010 and ADK ships ADK-009 for the same print() pattern. The framing is AutoGen's own rather than a port: The conversation itself is narrated to stdout, so a tool print lands mid-transcript and reads as though it were part of the exchange — when it is invisible to the agents reasoning over it.

What this PR does

1. Mirrors the new observability.yaml into testdata/rules-fixture/.
2. Adds cases to policyRuleCases, as TestPolicyRules_AllRulesCovered requires.

case	expectation
print("looking up " + order_id)	fires
logger.info("looking up %s", order_id)	silent
pprint({...})	silent

Three cases rather than two. The pprint case pins has_print_call's bare-callee behavior — the rule must not regress into substring matching that sweeps in pprint and every other callee whose name merely contains "print". The schema calls that out explicitly as the trap has_body_text falls into, so it's worth a standing test rather than a comment.

The silent case applies the remediation the fix text prescribes (a module logger) rather than deleting the call.

Verification

$ RULES_REPO=../trustabl-rules scripts/check-rules-sync.sh
rules fixture is in sync with production (87 files compared)

$ go vet ./internal/rules/
$ go test ./internal/rules/
ok  	github.com/trustabl/trustabl/internal/rules

[jhumel-code]

Thanks @bradAGI. I reviewed this together with trustabl/agent-reliability-rules#74, and the fixture copy is byte identical to the production pack, so the pair keeps rules-sync green as long as they merge together (and neither should land alone, as your PR body already says). The test cases are the part I want to call out. The pprint case is a genuinely useful pin, since PredHasPrintCall deliberately matches only the bare print callee and the schema comment names substring matching as the exact trap. I walked all three cases against the predicate on main: the fire case is a bare print call inside the tool body, the logging case is an attribute callee so it stays silent, and pprint is a different bare callee, so all three exercise real behavior rather than passing vacuously. Using the prescribed remediation (a module logger) as the silent input, instead of just deleting the call, is a nice touch too. The only stray bit is the unrelated blank-line removal at the end of policyRepoRuleCases, which is harmless. As noted on the rules half, AG2-018 will need a rationale doc in trustabl-rulebook before it ships; the maintainers can take that or pair on it. Approving, and I will coordinate landing the two halves together.