feat(plotly): implement streamline-basic (#2908)

## Implementation: `streamline-basic` - plotly

Implements the **plotly** version of `streamline-basic`.

**File:** `plots/streamline-basic/implementations/plotly.py`

**Parent Issue:** #2861

---
:robot: *[impl-generate
workflow](https://github.com/MarkusNeusinger/pyplots/actions/runs/20608632439)*

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

plots/streamline-basic/implementations/plotly.py

@@ -0,0 +1,74 @@
+""" pyplots.ai
+streamline-basic: Basic Streamline Plot
+Library: plotly 6.5.0 | Python 3.13.11
+Quality: 85/100 | Created: 2025-12-31
+"""
+
+import numpy as np
+import plotly.figure_factory as ff
+
+
+# Data - Create a grid for the vector field
+x = np.linspace(-3, 3, 30)
+y = np.linspace(-3, 3, 30)
+
+# Create vortex flow field: u = -y, v = x (circular streamlines)
+X, Y = np.meshgrid(x, y)
+
+# Simple vortex flow (no normalization - preserves velocity magnitude)
+u = -Y
+v = X
+
+# Create streamline plot with uniform color
+fig = ff.create_streamline(x, y, u, v, density=1.5, arrow_scale=0.08, line={"width": 2.5, "color": "#306998"})
+
+# Explicitly hide any colorbar that might be added
+for trace in fig.data:
+    if hasattr(trace, "showscale"):
+        trace.showscale = False
+    if hasattr(trace, "marker") and trace.marker is not None:
+        trace.marker.showscale = False
+
+# Update layout for large canvas with proper axis ranges matching data
+fig.update_layout(
+    title={"text": "streamline-basic · plotly · pyplots.ai", "font": {"size": 28}, "x": 0.5, "xanchor": "center"},
+    xaxis={
+        "title": {"text": "X Position (dimensionless)", "font": {"size": 22}},
+        "tickfont": {"size": 18},
+        "showgrid": True,
+        "gridwidth": 1,
+        "gridcolor": "rgba(0,0,0,0.1)",
+        "zeroline": True,
+        "zerolinewidth": 2,
+        "zerolinecolor": "rgba(0,0,0,0.3)",
+        "range": [-3.5, 3.5],
+        "autorange": False,
+    },
+    yaxis={
+        "title": {"text": "Y Position (dimensionless)", "font": {"size": 22}},
+        "tickfont": {"size": 18},
+        "showgrid": True,
+        "gridwidth": 1,
+        "gridcolor": "rgba(0,0,0,0.1)",
+        "zeroline": True,
+        "zerolinewidth": 2,
+        "zerolinecolor": "rgba(0,0,0,0.3)",
+        "range": [-3.5, 3.5],
+        "autorange": False,
+        "scaleanchor": "x",
+        "scaleratio": 1,
+    },
+    template="plotly_white",
+    margin={"l": 120, "r": 50, "t": 100, "b": 100},
+    plot_bgcolor="white",
+    showlegend=False,
+)
+
+# Hide any colorbar annotations or colorbars
+fig.update_coloraxes(showscale=False)
+
+# Save as PNG (4800 x 2700 px)
+fig.write_image("plot.png", width=1600, height=900, scale=3)
+
+# Save interactive HTML version
+fig.write_html("plot.html", include_plotlyjs="cdn")

plots/streamline-basic/metadata/plotly.yaml

@@ -0,0 +1,26 @@
+library: plotly
+specification_id: streamline-basic
+created: '2025-12-31T00:10:14Z'
+updated: '2025-12-31T00:30:31Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 20608632439
+issue: 2861
+python_version: 3.13.11
+library_version: 6.5.0
+preview_url: https://storage.googleapis.com/pyplots-images/plots/streamline-basic/plotly/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/streamline-basic/plotly/plot_thumb.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/streamline-basic/plotly/plot.html
+quality_score: 85
+review:
+  strengths:
+  - Clean vortex flow pattern clearly demonstrates streamline visualization
+  - Good use of plotly figure_factory for streamline generation
+  - Appropriate density parameter (1.5) creates balanced streamline distribution
+  - Correct title format and good font sizing throughout
+  - Interactive HTML output leverages plotly strength
+  - Equal aspect ratio (scaleanchor) preserves circular pattern correctly
+  weaknesses:
+  - Colorbar appears in rendered output despite multiple attempts to hide it in code
+    - creates visual clutter and misleading Velocity Magnitude label for uniform-colored
+    streamlines
+  - Layout asymmetry due to unwanted colorbar taking space on right side