Smart graph: option to show tags as nodes

[Leo310]

Resolves #288.

What

A new Scope → Tags toggle in the smart graph draws each tag as a node linked to every note that carries it, matching Obsidian's native graph with its Tags filter on.

• Tag nodes use the theme's --graph-node-tag colour, size by how many notes carry them, and show "N notes" in the tooltip.
• Clicking a tag node (or its context-menu entry) opens Obsidian's search on tag:#…, the same as clicking a tag in a note. The tag-search helper moved from MarkdownRenderer.svelte to utils/tagSearch.ts so chat and graph share it.
• Tag edges are undirected (no arrowheads) and always drawn when tags are shown, independent of the wiki/semantic link toggles.
• Tags match case-insensitively with the first-seen casing as label; a note mentioning a tag twice links to it once; nested tags are their own nodes.

Design: tags are a display layer

Tag nodes pull their notes together in the layout, but they never feed topic detection or the semantic scan:

• Edges are a new "tag" EdgeType; getTopicEdges and the isolated/bridge heuristics only read wiki/semantic edges, so topics are unchanged.
• graphTopologySignature ignores the tag layer, so flipping the toggle is a rebuild that hits every cache (partitions, hierarchy, ladder, semantic edges) instead of re-running Leiden.
• buildCollapsedGraph passes tag nodes through untouched (never folded into Unsorted, kind preserved), tag edges are re-pointed to topic bubbles but not counted as crossing links, and resolveNodePaths hands chat no path for a tag.
• applyWikiPatch diffs tag edges alongside wiki edges, so an unchanged tag layer stays a no-op and tag nodes never surface as added/removed/touched note paths.
• Note counts shown to the user, the semantic-scan ceiling and the drift threshold count notes only.
• A tag edge counts toward the tag's degree only (computeNodeDegrees, shared by the build, the fused recompute and the live patch). Note degree is the tie-breaker for topic representatives, so it stays exactly what it is without tags.

Verification

• bun run check, format, lint, and the full unit suite (1662 tests) pass; new tests cover the builder, live patch, collapse and signature behaviour.
• Live smoke in a slot vault: toggling the setting rebuilds the graph with green tag nodes and no console errors (screenshot below).

(Screenshot lives on the orphan branch assets/pr-graph-tag-nodes; delete it after merge.)

AI assistance: written with AI coding agents from the maintainer's brief; reviewed and tested by the maintainer.

[greptile-apps]

Greptile Summary

This PR adds an optional smart-graph display layer that represents tags as themed nodes connected to their notes.

• Adds tag-node construction, rendering, tooltips, search interactions, settings, and live graph updates.
• Keeps tag nodes and edges out of semantic scans, topic detection, representative selection, note counts, and chat paths.
• Preserves tags when topics are collapsed while excluding tag relationships from topic crossing-link counts.
• Centralizes degree calculation so tag edges size tag nodes without changing note degree or topic representatives.
• Adds focused tests for graph construction, topology signatures, live patches, collapsing, and degree behavior.

Confidence Score: 5/5

The PR appears safe to merge; no actionable new defect remains, and the previously reported topic-representative issue is fully fixed.

Tag edges now contribute degree only to tag nodes across full builds, semantic fusion, and live patches, so enabling tags no longer changes note degree or topic representatives. The remaining display-layer boundaries are consistently maintained.

Important Files Changed

Filename	Overview
src/views/smart-graph/graphDataBuilder.ts	Builds case-insensitive tag nodes and note-to-tag edges while keeping note degrees independent of tags.
src/components/graph/SmartGraphView.svelte	Integrates the tag setting into graph rebuilds, semantic filtering, note counts, live updates, and tag search.
src/components/graph/GraphCanvas.svelte	Adds tag-specific click, context-menu, preview, sizing, and edge handling.
src/components/graph/pixiRenderer.ts	Renders themed tag nodes and always-visible undirected tag edges with note-count tooltips.
src/utils/graphUtils.ts	Adds tag identity helpers, tag-independent topology signatures, and centralized degree computation.
src/utils/liveGraphPatch.ts	Includes tag-layer changes in live patches without exposing synthetic tag identifiers as note paths.
src/utils/mergeNodes.ts	Preserves tag nodes through topic collapsing and excludes them from note-path resolution.
src/utils/tagSearch.ts	Extracts the existing Obsidian tag-search behavior for reuse by chat and graph interactions.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    V[Filtered vault notes] --> W[Wiki edges]
    V --> S[Semantic edges]
    V --> G[Tag display layer]
    W --> T[Topic detection]
    S --> T
    W --> R[Graph rendering]
    S --> R
    G --> R
    G -. excluded .-> T
    G -. excluded .-> C[Semantic scan and chat paths]

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