uv dev environment, README writing pass, publish hygiene

- pyproject.toml + uv.lock: uv-managed dev environment (uv sync /
  uv run pytest). requirements.txt stays: KiCad builds the plugin's
  runtime venv from it and the PCM zip packages it.
- README: em-dash and run-on cleanup (34 -> 22, the rest deliberate),
  split the 120-word THT solder-joint sentence, fix the documented
  ADAPTIVE_MAX_CELL_UM value (2 mm -> 1 mm, config has 1000 um), fix
  the *Packaging / publishing* cross-reference, dev sections now use
  uv sync / uv run.
- LLM disclaimer: "most commits" carry the trailer (32 of 39), figures
  claim now excepts the hand-drawn hole cross-section, reference the
  UT3513+ measured-vs-computed validation.
- .gitignore: local AI-tooling artifacts; deploy scripts exclude
  pyproject.toml/uv.lock; error-figure title punctuation aligned with
  the other window titles.

fill_resistance/plots.py

@@ -416,7 +416,7 @@ def fig_power(result, stack, e1, e2, problem):
 def fig_error(message: str):
     fig, ax = plt.subplots(figsize=(9, 4.5), layout="constrained")
     ax.axis("off")
-    ax.set_title("Fill Resistance — ERROR", color="#b02a2a",
+    ax.set_title("Fill Resistance - ERROR", color="#b02a2a",
                  fontsize=14, fontweight="bold", loc="left")
     wrapped = "\n".join(
         textwrap.fill(line, width=90) for line in message.splitlines()