chore: nudge ci on plugin-only PR

This PR only touches mem0-plugin/, which is outside the path filters
in .github/workflows/ci.yml — but branch protection requires
build_mem0 and build_embedchain status checks to merge. Add a
clarifying comment in pyproject.toml so the workflow triggers
once and posts the required statuses.

Follow-up: branch protection should be reconfigured so plugin-only
PRs don't need this nudge.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -153,3 +153,4 @@ known-first-party = ["mem0", "mem0_cli"]
 [tool.isort]
 profile = "black"
 known_first_party = ["mem0", "mem0_cli"]
+# isort scope kept aligned with [tool.ruff.lint.isort] above.