fix: remove backend-path to resolve ValueError: paths must be inside source tree

python -m build fails in CI with:
  ValueError: paths must be inside source tree

This is thrown by pyproject_hooks.BuildBackendHookCaller.__init__ which
validates that all backend-path entries resolve inside the package source
directory. The backend-path = ["../../versioning/helper"] in each package's
pyproject.toml points outside the package tree, triggering this check before
any build code runs. Setting PYTHONPATH has no effect since the error fires
during path validation, not import.

Fix: remove backend-path from all 14 packages. The CI pipeline already exports
PYTHONPATH="${ROOT_DIR}/versioning/helper" which makes build_backend importable
in the hook subprocess. The custom backend and its S360 version constraint
injection are unaffected. uv build from the repo root continues to work for
local development.

Author: sellakumaran

libraries/microsoft-agents-a365-notifications/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-notifications"

libraries/microsoft-agents-a365-observability-core/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-observability-core"

libraries/microsoft-agents-a365-observability-extensions-agentframework/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-observability-extensions-agent-framework"

libraries/microsoft-agents-a365-observability-extensions-langchain/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-observability-extensions-langchain"

libraries/microsoft-agents-a365-observability-extensions-openai/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-observability-extensions-openai"

libraries/microsoft-agents-a365-observability-extensions-semantickernel/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-observability-extensions-semantic-kernel"

libraries/microsoft-agents-a365-observability-hosting/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-observability-hosting"

libraries/microsoft-agents-a365-runtime/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-runtime"

libraries/microsoft-agents-a365-tooling-extensions-agentframework/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-tooling-extensions-agentframework"

libraries/microsoft-agents-a365-tooling-extensions-azureaifoundry/pyproject.toml

@@ -1,7 +1,6 @@
 [build-system]
 requires = ["setuptools>=68", "wheel", "tzdata", "tomlkit", "packaging"]
 build-backend = "build_backend"
-backend-path = ["../../versioning/helper"]
 
 [project]
 name = "microsoft-agents-a365-tooling-extensions-azureaifoundry"