Expand `/run-tests` venv pre-flight to cover all cases

Rework section 3 from a worktree-only check into a
structured 3-step flow: detect active venv, interpret
results (Case A: active, B: none, C: worktree), then
run import + collection checks.

Deats,
- Case B prompts via `AskUserQuestion` when no venv
  is detected, offering `uv sync` or manual activate
- add `uv run` fallback section for envs where venv
  activation isn't practical
- new allowed-tools: `uv run python`, `uv run pytest`,
  `uv pip show`, `AskUserQuestion`

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

.claude/skills/run-tests/SKILL.md

@@ -8,8 +8,11 @@ allowed-tools:
   - Bash(python -m pytest *)
   - Bash(python -c *)
   - Bash(python --version *)
-  - Bash(git rev-parse *)
+  - Bash(UV_PROJECT_ENVIRONMENT=py* uv run python *)
+  - Bash(UV_PROJECT_ENVIRONMENT=py* uv run pytest *)
   - Bash(UV_PROJECT_ENVIRONMENT=py* uv sync *)
+  - Bash(UV_PROJECT_ENVIRONMENT=py* uv pip show *)
+  - Bash(git rev-parse *)
   - Bash(ls *)
   - Bash(cat *)
   - Bash(jq * .pytest_cache/*)
@@ -17,6 +20,7 @@ allowed-tools:
   - Grep
   - Glob
   - Task
+  - AskUserQuestion
 ---
 
 Run the `tractor` test suite using `pytest`. Follow this
@@ -91,41 +95,104 @@ python -m pytest tests/ -x --tb=short --no-header --tpt-proto uds
 python -m pytest tests/ -x --tb=short --no-header -k "cancel and not slow"
 ```
 
-## 3. Pre-flight checks (before running tests)
+## 3. Pre-flight: venv detection (MANDATORY)
 
-### Worktree venv detection
+**Always verify a `uv` venv is active before running
+`python` or `pytest`.** This project uses
+`UV_PROJECT_ENVIRONMENT=py<MINOR>` naming (e.g.
+`py313`) — never `.venv`.
 
-If running inside a git worktree (`git rev-parse
+### Step 1: detect active venv
---git-common-dir` differs from `--git-dir`), verify
+
-the Python being used is from the **worktree's own
+Run this check first:
-venv**, not the main repo's. Check:
+
+```sh
+python -c "
+import sys, os
+venv = os.environ.get('VIRTUAL_ENV', '')
+prefix = sys.prefix
+print(f'VIRTUAL_ENV={venv}')
+print(f'sys.prefix={prefix}')
+print(f'executable={sys.executable}')
+"
+```
+
+### Step 2: interpret results
+
+**Case A — venv is active** (`VIRTUAL_ENV` is set
+and points to a `py<MINOR>/` dir under the project
+root or worktree):
+
+Use bare `python` / `python -m pytest` for all
+commands. This is the normal, fast path.
+
+**Case B — no venv active** (`VIRTUAL_ENV` is empty
+or `sys.prefix` points to a system Python):
+
+Use `AskUserQuestion` to ask the user:
+
+> "No uv venv is active. Should I activate one
+> via `UV_PROJECT_ENVIRONMENT=py<MINOR> uv sync`,
+> or would you prefer to activate your shell venv
+> first?"
+
+Options:
+1. **"Create/sync venv"** — run
+   `UV_PROJECT_ENVIRONMENT=py<MINOR> uv sync` where
+   `<MINOR>` is detected from `python --version`
+   (e.g. `313` for 3.13). Then use
+   `py<MINOR>/bin/python` for all subsequent
+   commands in this session.
+2. **"I'll activate it myself"** — stop and let the
+   user `source py<MINOR>/bin/activate` or similar.
+
+**Case C — inside a git worktree** (`git rev-parse
+--git-common-dir` differs from `--git-dir`):
+
+Verify Python resolves from the **worktree's own
+venv**, not the main repo's:
 
 ```sh
 python -c "import tractor; print(tractor.__file__)"
 ```
 
-If the path points outside the worktree (e.g. to
+If the path points outside the worktree, create a
-the main repo), set up a local venv first:
+worktree-local venv:
 
 ```sh
 UV_PROJECT_ENVIRONMENT=py<MINOR> uv sync
 ```
 
-where `<MINOR>` matches the active cpython minor
+Then use `py<MINOR>/bin/python` for all commands.
-version (detect via `python --version`, e.g.
-`py313` for 3.13, `py314` for 3.14). Then use
-`py<MINOR>/bin/python` for all subsequent commands.
 
-**Why this matters**: without a worktree-local venv,
+**Why this matters**: without the correct venv,
-subprocesses spawned by tractor resolve modules from
+subprocesses spawned by tractor resolve modules
-the main repo's editable install, causing spurious
+from the wrong editable install, causing spurious
-`AttributeError` / `ModuleNotFoundError` for code
+`AttributeError` / `ModuleNotFoundError`.
-that only exists on the worktree's branch.
 
-### Import + collection checks
+### Fallback: `uv run`
 
-Always run these, especially after refactors or
+If the user can't or won't activate a venv, all
-module moves — they catch import errors instantly:
+`python` and `pytest` commands can be prefixed
+with `UV_PROJECT_ENVIRONMENT=py<MINOR> uv run`:
+
+```sh
+# instead of: python -m pytest tests/ -x
+UV_PROJECT_ENVIRONMENT=py313 uv run pytest tests/ -x
+
+# instead of: python -c 'import tractor'
+UV_PROJECT_ENVIRONMENT=py313 uv run python -c 'import tractor'
+```
+
+`uv run` auto-discovers the project and venv,
+but is slower than a pre-activated venv due to
+lock-file resolution on each invocation. Prefer
+activating the venv when possible.
+
+### Step 3: import + collection checks
+
+After venv is confirmed, always run these
+(especially after refactors or module moves):
 
 ```sh
 # 1. package import smoke check