docs: correct M0 publisher endpoint (#311)

Co-authored-by: Codex <noreply@openai.com>

Author: Pigbibi

docs/m0_research_publisher_envelope_contract.md

@@ -70,7 +70,7 @@ metadata 的便利方式，构建器不会执行 shell 或命令替换。
 构建器才会在成功写入本地封套后对 HTTPS endpoint 进行一次 POST：
 
 ```bash
-export QSL_M0_RESEARCH_LEDGER_PUBLISH_URL='https://research-console.example/api/internal/m0'
+export QSL_M0_RESEARCH_LEDGER_PUBLISH_URL='https://research-console.example/api/internal/sync-m0-research-ledger'
 export QSL_M0_RESEARCH_LEDGER_PUBLISH_TOKEN='dedicated-publisher-token'
 
 python3 python/scripts/build_m0_research_publisher_envelope.py ... --publish

python/tests/test_build_m0_research_publisher_envelope.py

@@ -264,7 +264,7 @@ def fake_urlopen(request, timeout):
             publisher.publish_m0_research_publisher_envelope(
                 envelope,
                 environ={
-                    publisher.PUBLISH_URL_ENV: "https://research-console.example/api/internal/m0",
+                    publisher.PUBLISH_URL_ENV: "https://research-console.example/api/internal/sync-m0-research-ledger",
                     publisher.PUBLISH_TOKEN_ENV: secret,
                     "BROKER_API_TOKEN": "must-not-be-read",
                 },