Network File and Explorer: Load data for edges; show colored and labelled edges

[janezd]

Issue

Resolves #247.

Description of changes

• Add edge annotation to Pajek files. This is a "non-standard" extension to a largely undocumented format.
• File widget: add input tables for label and edge annotation.
• File widget: implement construction of networks from table of edges if file is not present.
• Network explorer: color and label edges.

Includes

• Code changes
• Tests
• Documentation

[codecov-commenter]

Codecov Report

Patch coverage: 92.70% and project coverage change: +4.06 🎉

Comparison is base (3496707) 73.34% compared to head (eb3ad0e) 77.40%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #249      +/-   ##
==========================================
+ Coverage   73.34%   77.40%   +4.06%     
==========================================
  Files          21       26       +5     
  Lines        2975     3581     +606     
==========================================
+ Hits         2182     2772     +590     
- Misses        793      809      +16     

Impacted Files	Coverage Δ
...gecontrib/network/network/tests/test_embeddings.py	100.00% <ø> (ø)
...rangecontrib/network/network/tests/test_twomode.py	100.00% <ø> (ø)
orangecontrib/network/widgets/graphview.py	66.43% <60.00%> (-0.60%)	⬇️
orangecontrib/network/widgets/OWNxExplorer.py	67.60% <73.33%> (-0.07%)	⬇️
orangecontrib/network/widgets/OWNxFile.py	95.62% <97.57%> (+9.36%)	⬆️
orangecontrib/network/network/base.py	81.08% <100.00%> (ø)
orangecontrib/network/network/compose.py	100.00% <100.00%> (ø)
orangecontrib/network/network/readwrite.py	82.43% <100.00%> (+1.00%)	⬆️
...rangecontrib/network/network/tests/test_compose.py	100.00% <100.00%> (ø)
...ngecontrib/network/network/tests/test_readwrite.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[Copilot]

Pull request overview

This PR expands Orange3-Network’s network IO and visualization capabilities by (1) supporting edge labels in Pajek-like .net files and (2) allowing networks to be constructed/annotated from input node/edge tables, with corresponding UI updates in Network File and Network Explorer.

Changes:

• Added network.compose utilities and integrated them into OWNxFile to construct/annotate networks from input tables (including edge-table matching).
• Updated OWNxExplorer + GraphView to support selecting edge label/color/width sources (including “Weights”) and render per-edge colors/widths/labels.
• Added/updated extensive tests, sample network/data files, and documentation/i18n strings.

Reviewed changes

Copilot reviewed 18 out of 28 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
orangecontrib/network/widgets/tests/test_ownxsinglemode.py	Adjust test to avoid mutating shared node table state.
orangecontrib/network/widgets/tests/test_OWNxFile.py	Major new test coverage for new OWNxFile behaviors (items/edges inputs, hints, composing, warnings/errors).
orangecontrib/network/widgets/tests/test_OWNxExplorer.py	Update tests for new edge-label selection mechanism (“Weights”).
orangecontrib/network/widgets/tests/networks/test-compose.net	Adds a test network used by new widget flow tests.
orangecontrib/network/widgets/OWNxFile.py	Adds “construct from inputs” mode; edge input; hint-based variable persistence; edge annotation matching; reporting updates.
orangecontrib/network/widgets/OWNxExplorer.py	Adds edge label/color/width controls + hint persistence; supplies edge labels/widths/colors to GraphView.
orangecontrib/network/widgets/graphview.py	Adds per-edge color support; refactors edge width/label rendering to query widget for labels/widths/colors.
orangecontrib/network/networks/stations.xlsx	Adds a bundled dataset (binary).
orangecontrib/network/networks/railway.xlsx	Adds a bundled dataset (binary).
orangecontrib/network/networks/railway.net	Adds a bundled sample network file.
orangecontrib/network/networks/lastfm.tab	Updates bundled tab metadata (class header row).
orangecontrib/network/network/tests/towns.net	Adds a test network with edge labels for read/write tests.
orangecontrib/network/network/tests/test-arcslist.net	Adds a Pajek arcslist test fixture.
orangecontrib/network/network/tests/test_twomode.py	Adds tests for two-mode to single-mode conversion/weighting.
orangecontrib/network/network/tests/test_readwrite.py	Switch to importlib.resources for packaged fixtures; adds edge-label read test.
orangecontrib/network/network/tests/test_embeddings.py	Adds Node2Vec tests gated on gensim availability.
orangecontrib/network/network/tests/test_compose.py	Adds unit tests for new compose utilities (tables → network).
orangecontrib/network/network/tests/init.py	Present in PR listing (no functional changes shown).
orangecontrib/network/network/readwrite.py	Extends edge parsing to support non-numeric edge labels (returns edge_data alongside weights).
orangecontrib/network/network/compose.py	New module: construct networks from node/edge tables; validation helpers and errors.
orangecontrib/network/network/base.py	Updates edge-data documentation; adjusts undirected twoway-edge computation behavior.
i18n/si/msgs.jaml	Adds new strings for compose + updated widget UI/labels.
doc/widgets/networkfile.md	Updates widget docs for new inputs and “construct from tables” workflow.
doc/widgets/networkexplorer.md	Updates explorer docs to match new UI layout and edge controls.
doc/widgets/images/Network-File-stamped.png	Adds/updates widget screenshot (binary).

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