Split filtering, add reference-stable index, and reconcile the canvas

[kmcginnes]

Task

Split filtering from conversion, add a reusable reference-stable index, and replace the full-replace + structure-version counter with a pure reconciler. This is one behavioral change — the graph stops rebuilding on every update — so the split, the memo, and the reconciler ship together.

Details

Filtering (presence) as its own concept:

• A hook returning the surviving source Vertex[] (reads node filter state; answers only "is this vertex present?").
• A hook returning the surviving source Edge[] (reads edge filter state + endpoint existence).

Conversion — pure total functions: Vertex → Canvas Vertex, Edge → Canvas Edge. No branches, no filtering, no volatile fields.

Reference-stable index — reusable util: maps each source item to an output, reusing the previous output when the source reference is unchanged; absent keys are evicted for free. Held in a ref so it persists across renders. Simultaneously the diff mirror, converter cache, and carry-forward index. Used by both the Graph View and Schema View.

Reconciler (internal seams, not exported from the module barrel):

• Pure diffElements(prev, next) returning { added, removed, updated }, keyed on id presence + reference identity: same id + same ref → skip; same id + different ref → update (remove + add); new id → add; missing id → remove.
• Thin applyDelta(cy, delta): one batch doing removes, node-adds before edge-adds, updates as remove-then-add. No patching, no data inspection.
• The element-update hook becomes diff → apply → advance index → return { addedNodeIds, structureRevision }. addedNodeIds = genuinely-new vertices only.

Retire the structure-version counter:

• Layout reads addedNodeIds; delete its previous-nodes bookkeeping.
• Visibility, lock, blast-radius, connections-filter depend on the structureRevision token.
• Delete the phantom counter prop from the selection hook.
• Delete the deep-clone and full-replace.

Schema View: same three-part shape (presence = existing endpoint-existence check; conversion = vertex-type-config → element; shared reference-stable index).

Acceptance

• Expanding one neighbor adds one vertex; layout positions only the new vertex; existing positions preserved.
• diffElements unit tests: add, remove, update (ref change → remove+add), unchanged (same ref → skip), node-before-edge ordering, empty↔populated, no-op → empty delta.
• applyDelta tests against a headless Cytoscape (or fake): batch add/remove/re-add, never patches.
• Reference-stable index tests: same ref → same output; changed ref → new output; dropped key → evicted.
• No deep-clone or full-replace remains; the structure-version counter is gone.
• pnpm check:types and pnpm test green.

Related Issues

• Parent Reconcile the graph canvas — stop rebuilding on every change #1887
• Blocked by the decouple task

Important

Internal only — this issue is maintained by the core team and is not accepting external contributions.