propose: @FeignClient is a caller, not an exposer (#25)

* propose: @FeignClient is a caller, not an exposer

Reported-by: review on cross_service_smoke

A @FeignClient method is a client — it makes outbound HTTP calls.
But the indexer emits an EXPOSES edge from every Feign method to a
consumer-side Route node, treating the caller as if it also exposed
the endpoint. The same wire ends up represented as two unrelated
Route nodes (one consumer-side in the caller, one endpoint-side in
the server) and the HTTP_CALLS edge lands on the wrong one,
producing intra_service match labels for what are really
cross-service calls.

The root cause: ast_java.py:2178 already distinguishes
kind=http_consumer (Feign) from kind=http_endpoint (Controller),
but build_ast_graph.py:1354-1364 emits EXPOSES unconditionally per
RouteDecl. The semantic distinction was made; it's just not
honoured at emission.

Single-PR fix (~150 LOC): suppress EXPOSES emission when
kind=http_consumer, extend the cross-service matcher to pair
consumer Routes against endpoint Routes across microservices,
add pass4_feign_exposes_suppressed counter to graph_meta with
new _META_PR_FEIGN tier.

Status: draft. Six [TBD] items including a recommendation to
audit ASYNC_CALLS for the symmetric bug before implementation.

* propose: fold ASYNC_CALLS audit verdict into §8 and [TBD-6]

Audited all five RouteDecl emission sites in ast_java.py for the
symmetric Feign-style EXPOSES bug. Verdict: bug does not exist on
the async side. Async uses structurally different annotations per
direction (@KafkaListener consumer vs KafkaTemplate.send producer);
only listeners emit RouteDecl, producers emit OutgoingCall. Verified
empirically on cross_service_smoke fixture. Fix stays HTTP-only.

Author: HumanBean17