[Subtask] Support bulk editing of node and edge attributes

[oxy86]

Overview

Introduce bulk editing capabilities for node and edge attributes, allowing users to modify multiple elements at once.

This builds on the table view (#225) and attribute editing (#224), enabling efficient data cleaning and transformation workflows.

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Motivation

Editing attributes one node/edge at a time is not practical for real-world datasets.

Users need to:

• update many nodes at once
• assign values to groups
• clean or normalize data

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Scope

Bulk operations

• set attribute value for selected nodes/edges
• add attribute to multiple elements
• remove attribute from multiple elements

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Selection sources

• manually selected nodes/edges
• filtered results ([Feature] Graph filtering, querying & subgraph extraction #215)
• table view selections ([Subtask] Add structured table views for nodes and edges #225)

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Behavior

• operations apply to:
  • current selection
  • or visible subset
• must be:
  • non-destructive where possible (undo-friendly)
  • consistent with attribute system ([Feature Request] Custom Attributes for Nodes and Edges (Incl. Dates) #96)

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UI Suggestions

• context menu:
  • "Set attribute for selection"
• bulk edit dialog:
  • attribute name
  • value
• integration with table view:
  • multi-row edit

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Implementation Notes

• build on:
  • [Subtask] Improve and unify node/edge attribute editing in the UI #224 Attribute editing
  • [Subtask] Add structured table views for nodes and edges #225 Table view
• ensure updates trigger UI refresh correctly
• prepare for future transformations (next subtask)

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Edge Cases

• mixed attribute types
• partially missing attributes
• large selections

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Dependencies

• [Subtask] Improve and unify node/edge attribute editing in the UI #224 Attribute editing UI
• [Subtask] Add structured table views for nodes and edges #225 Table view

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Relation to Feature

Part of:
#223 Graph data editing and structured data workflows