Scope graph-view and schema-view layouts to the browser tab

[kmcginnes]

Description

The graph-view and schema-view layout state (active sidebar tab, sidebar width, view toggles, details-auto-open preference) was persisted as a single localForage value shared across all browser tabs. Opening the app in a second tab clobbered the first tab's layout — last-writer-wins over the whole value.

This scopes both layouts to the browser tab using the same per-tab mechanism the active connection already uses: the live value lives in sessionStorage (survives this tab's reload, never leaks to other tabs), with a shared localForage breadcrumb that seeds a freshly-opened tab from the last-used layout on cold start.

Core change: the per-tab + breadcrumb "trick" that was inlined in activeConnectionStorage.ts is extracted into a generic createSessionScopedAtom<T>. createActiveConfigurationAtom is refactored onto it (so the subtle seed-and-claim logic lives in one place), and both layout atoms now route through it with zod-validated codecs.

Notable details:

• zod-validated per-tab reads. sessionStorage holds strings, so each layout has a codec. deserialize returns null for an absent value but throws on a corrupt/wrong-shape one; the seam (createSessionScopedAtom) catches, logs, and falls back to the breadcrumb then the default — so a stale or hand-edited value can never crash the top-level-await startup. Detecting corruption is kept separate from deciding what to do about it.
• Set serialization. Graph-view's activeToggles is a runtime Set; its codec serializes it as an array for JSON and rebuilds the Set on read. Schema-view is plain JSON.
• No migration. The breadcrumb keeps each concept's existing localForage key and shape, so existing stored layouts seed a fresh tab unchanged.

The new per-tab scope is recorded in an ADR alongside the two existing shared scopes (reconciled maps, blind-write scalars).

Validation

• pnpm checks passes (types, lint, format).
• pnpm test passes (full suite, 2086 tests), including new coverage in sessionScopedStorage.test.ts (seed order, corrupt-value + SecurityError recovery, the Set-bearing cold-start claim, and cross-tab isolation/seeding through the real graph-view and schema-view codecs).
• Reviewer focus: confirm the seeding order (this tab's sessionStorage → shared breadcrumb → default), that a corrupt per-tab value recovers instead of crashing, and that graph-view's activeToggles Set round-trips across a write-then-cold-start sequence.

How to read

1. packages/graph-explorer/src/core/StateProvider/sessionScopedStorage.ts — start here; the extracted per-tab primitive (seed → claim → write-through) plus parseSessionJson and the corrupt-value recovery seam
2. packages/graph-explorer/src/core/StateProvider/activeConnectionStorage.ts — the previously-inlined trick, now a thin wrapper over the primitive (behavior-preserving refactor)
3. packages/graph-explorer/src/core/StateProvider/graphViewLayoutDefaults.ts — the graph-view codec; the activeToggles Set ↔ array serialization
4. packages/graph-explorer/src/core/StateProvider/schemaViewLayoutDefaults.ts — the schema-view codec (plain JSON)
5. packages/graph-explorer/src/core/StateProvider/storageAtoms.ts — wires both layout atoms onto the primitive
6. docs/adr/20260630-per-tab-session-scoped-storage-primitive.md — the storage-scope decision and the three named scopes

Related Issues

• Related to Spike: deep-module restructuring of the storage-atom persistence layer #1876 (spike to formalize the storage-scope primitives)

Check List

• I confirm that my contribution is made under the terms of the Apache 2.0 license.
• I have verified pnpm checks passes with no errors.
• I have verified pnpm test passes with no failures.
• I have covered new added functionality with unit tests if necessary.
• I have updated documentation if necessary.