feat: read build-details.json (PEP 739) for version detection (Fixes #449)

Python 3.14+ ships a build-details.json file in the platform-independent stdlib directory. Use it as a faster, more authoritative source than parsing patchlevel.h headers, slotting it between pyvenv.cfg and the existing header-based fallback in the version detection chain.

Author: karthiknadig

Cargo.lock

@@ -18,6 +18,9 @@ serde_json = "1.0.93"
 sha2 = "0.10.6"
 env_logger = "0.10.2"
 
+[dev-dependencies]
+tempfile = "3.10"
+
 [features]
 ci = []
 ci-jupyter-container = []