fix: let assembly defects pierce the gate wrappers

Independent verification caught that the split shipped in the previous
commit did not actually hold on the only path production uses. The gate
wrappers re-raise GovernanceBackendError but nothing else, so
SourceNotConfiguredError fell into the following `except Exception` and
came back out as a governance_backend_down failure with retry_after_s=5.0.
A misconfigured source name would still retry forever and never surface.

The existing tests missed it because both of them call the private _cfg()
directly, one layer below the wrapper the governance loops actually go
through. The regression test goes through QuotaGate.

telemetry.py has to widen its terminal catch in the same commit: once the
wrapper stops relabeling the error, it is no longer a GovernanceBackendError,
and it is raised before any attempt exists, so the path would have recorded
no telemetry at all.

Also corrects the leak path count from three to five. QuotaGate.stats and
BreakerGate.retry_after_s are not wrapped by _record_quietly either.

CHANGELOG.md

@@ -19,8 +19,8 @@
 
 ### 下游请读
 
-- **`GovernanceBackendError` 现携带 `scope` / `reason` / `retry_after_s` / `per_source_reasons`**,与 `AllSourcesExhausted` 同款;`str(exc)` 仍是原来的诊断串(如 `限流后端 try_acquire 失败: ...`),结构化字段与诊断信息并存,排障不受影响。
-- **三条闸门路径**(`try_acquire` / `try_enter` / `progress_age_s`)的后端故障会到达调用方;记账路径(`record_success` 等)仍被 `_record_quietly` 降级为 warning,这个分工不变。
+- **`GovernanceBackendError` 现携带 `scope` / `reason` / `retry_after_s`**,与 `AllSourcesExhausted` 同款(`per_source_reasons` 属性存在但恒为 `{}`——后端故障不针对具体某个源);`str(exc)` 仍是原来的诊断串(如 `限流后端 try_acquire 失败: ...`),结构化字段与诊断信息并存,排障不受影响。
+- **五条闸门路径**的后端故障会到达调用方: `QuotaGate` 的 `try_acquire` / `stats` / `progress_age_s`,`BreakerGate` 的 `try_enter` / `retry_after_s`。记账路径(`record_success` / `record_failure` / `release_probe` / `mark_progress`)仍被 `_record_quietly` 降级为 warning,这个分工不变。
 - **CHSAnalyzer 迁移**: `tracking.py` 一条 `except GatewayUnavailableError` 即覆盖完整,无需为后端故障单列分支(`migrations/chsanalyzer.md` G1 已补注)。
 
 ## 1.0.6(2026-08-02)