Add scalene profiling wrapper as opt-in dependency group (#507)

* Add scalene profiling wrapper as opt-in dependency group

Adds scripts/profile_with_scalene.py: a thin CLI wrapper around Scalene
2.2's `run` and `view` subcommands. Accepts .py or .ipynb targets,
auto-converts notebooks via nbconvert (with an injected IPython stub so
magic calls survive the conversion), and writes self-contained HTML or
JSON reports under artifacts/scalene/.

Scalene + nbconvert live in a new [dependency-groups.profiling] entry
in pyproject.toml, so default `uv sync` is unaffected — production
installs do not pay the profiler's cost. To use:

  uv sync --group profiling
  uv run python scripts/profile_with_scalene.py path/to/script.py
  uv run python scripts/profile_with_scalene.py tutorials/audio/x.ipynb

Tests in src/tests/scripts/profile_with_scalene_test.py are guarded by
@pytest.mark.skipif(not scalene_available), so they silently skip on the
default install path and the existing CI suite is unchanged.

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

* Inject IPython stub after __future__ imports in converted notebooks

Notebooks containing `from __future__ import annotations` (or any other
__future__ import) failed to profile because the IPython stub was
prepended to the converted .py, pushing the __future__ imports past line
1 and triggering a SyntaxError.

Fix: walk the converted source for `from __future__` lines and insert
the stub after the last one. When no future imports are present, the
stub still goes at the very top.

Adds a regression test using a synthetic notebook whose first cell line
is `from __future__ import annotations`.

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

---------

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

Author: satra

pyproject.toml

@@ -108,6 +108,10 @@ dev = [
 docs = [
   "pdoc~=16.0"
 ]
+profiling = [
+  "scalene>=2.2",
+  "nbconvert>=7"
+]
 
 [tool.hatch.build.targets.wheel]
 packages = ["src/senselab"]