Harden L7 control plane repair and steering visibility

[kacy]

Summary

• broaden the periodic L7 control-plane loop so it repairs route materialization even before VIP cutover
• expose control-plane steering state separately from overall L7 control-plane state
• surface steering drift and control-plane trigger details in service and rollout status
• add end-to-end repair coverage for both event-driven and periodic listener-path recovery

Testing

• timeout 45 env YOQ_SKIP_SLOW_TESTS=1 ZIG_GLOBAL_CACHE_DIR=/tmp/yoq-zig-global-cache ZIG_LOCAL_CACHE_DIR=/tmp/yoq-zig-local-cache zig build test -Doptimize=ReleaseSafe -- --test-filter "periodic control plane repairs routes without vip steering"
• timeout 45 env YOQ_SKIP_SLOW_TESTS=1 ZIG_GLOBAL_CACHE_DIR=/tmp/yoq-zig-global-cache ZIG_LOCAL_CACHE_DIR=/tmp/yoq-zig-local-cache zig build test -Doptimize=ReleaseSafe -- --test-filter "mapped listener target serves proxied HTTP after event-driven repair"
• timeout 45 env YOQ_SKIP_SLOW_TESTS=1 ZIG_GLOBAL_CACHE_DIR=/tmp/yoq-zig-global-cache ZIG_LOCAL_CACHE_DIR=/tmp/yoq-zig-local-cache zig build test -Doptimize=ReleaseSafe -- --test-filter "periodic repair restores mapped listener target and serves proxied HTTP"
• timeout 45 env YOQ_SKIP_SLOW_TESTS=1 ZIG_GLOBAL_CACHE_DIR=/tmp/yoq-zig-global-cache ZIG_LOCAL_CACHE_DIR=/tmp/yoq-zig-local-cache zig build test -Doptimize=ReleaseSafe -- --test-filter "route handles /v1/status?mode=service_rollout GET"
• timeout 45 env YOQ_SKIP_SLOW_TESTS=1 ZIG_GLOBAL_CACHE_DIR=/tmp/yoq-zig-global-cache ZIG_LOCAL_CACHE_DIR=/tmp/yoq-zig-local-cache zig build test -Doptimize=ReleaseSafe -- --test-filter "handleMetricsPrometheus exposes service rollout metrics"

Each targeted run hit the explicit timeout without emitted failures.