♻️ Rework project-uv probe for cross-platform determinism

Probe now emits KEY=VALUE so the agent reads facts instead of inferring
from prose. Stdlib-only (no tomllib) so it runs on whatever Python the
launcher reaches. Adds sh/ps1 launcher pair, SCRIPTS_UV/SCRIPTS_DIR/
SCRIPTS_STORE env-var contract, tainted-venv + recipe + default-package
detection, and broader mode classification (incl. agent-tool-only).
SKILL.md trimmed and gated by pyproject.toml glob.

docs/workpad/goals/uv_detection.md

@@ -25,3 +25,5 @@
 - it should also therefore get the idea of where a local scratch pad (SCRIPTS_STORE), project scripts folder (SCRIPTS_DIR), etc. might exist, and can therefore substitute this also as knowledge if it has to work with other tools, that want files or scripts written, but do not define where a certain folder is. These directories build good fallbacks for such concerns, and python therefore a solid tool to support the developer in tasks.
 - for full python projects, it is very likely, that the configured uv is also capable of running actual project code, so namespaces should be respected.
 - for rust projects, the uv configuration is almost certainly the local python environment for the agent.
+
+- best would be if we would simply run a universal shell that every skill should support and print out env variables that are maybe relevant immediately.