lower the python floor to 3.12

Fixes #26.

`requires-python` was `>=3.14`. On anything older poetry declines to create an
environment, and it says so on stderr while leaving stdout empty. The README
tells the user to run `iex (poetry env activate)`, `iex` only sees stdout, and
PowerShell reports

    Invoke-Expression : Cannot bind argument to parameter 'Command' because it
    is null.

which points at `iex` rather than at the install that never happened. The
first reply on the issue guessed the reporter was missing `iex`, which is a
built-in alias, so the error is actively misleading.

3.14 looks stricter than anything the code needs. Every file in src/ compiles
on 3.10, no 3.13 or 3.14 only syntax appears anywhere in the tree, and the
full task set was run end to end on 3.12.10 against a live account with all
six tasks completing. The dependency graph agrees: numpy is the highest floor
in the lock at >=3.12, so 3.12 is where the real constraint sits.

Verified after the change on 3.12.10: `poetry install` creates the
environment, `poetry env activate` emits a real activation command instead of
nothing, `iex (poetry env activate)` activates in PowerShell, and every
dependency plus every module under src/ imports.

The lock is regenerated rather than left stale, since `requires-python` feeds
its content hash. The only substantive change is a typing_extensions marker
for python_version < 3.13; the package set is unchanged at 203. Regenerated
with poetry 2.4.1 to match the version that wrote the existing file.

The README gains the version bump and a short note on the failure, so anyone
who hits it while running an older Python can recognise it.

README.md

@@ -24,7 +24,9 @@ You should also have an Ollama account created (for the LLM), the `ollama` tool
 You must also provide an image for the script to upload to complete the visual search task. Currently, this image is named `keypress_times.png` and is located in the root directory of the project (yes, I used a random image from my keyboard analysis to do this). You may provide an image of your own, just ensure that the absolute path of the image is placed in the `VISUAL_SEARCH_IMAGE_PATH` constant at the top of `rewards_tasks.py`.
 
 Activate the virtual environment & install dependencies (you may have to use `python -m poetry` instead of `poetry`).
-You must have Python 3.14+ and Poetry installed.
+You must have Python 3.12+ and Poetry installed.
+
+If `iex (poetry env activate)` fails with *"Cannot bind argument to parameter 'Command' because it is null"*, `poetry install` did not create an environment. Run `python --version` first: an older Python leaves poetry with nothing to activate, and the message explaining that goes to stderr rather than into `iex`.
 
 Windows (PowerShell)
 ```sh