Export, import and sequence graph views as shareable artifacts

[paolino]

Summary

Turn a shaped graph into a shareable view artifact (file or URL), let users import it to reproduce the exact visible set, edges, and node positions, and compose several views into an ordered sequence (narrative tour / slides).

Spec

specs/013-view-export-import/spec.md on branch 013-view-export-import (worktree /code/graph-browser-view-export-import/).

User stories

• P1 — Export the current view as a self-contained artifact (file and URL forms), human-readable, no secrets.
• P1 — Import a view artifact (from file or URL); imported view is fully interactive, not a read-only snapshot.
• P1 — Graceful degradation when the underlying graph data has diverged: render what resolves, report what doesn't, never silently fail.
• P2 — Compose exported views into an ordered sequence (tour/slides), itself a shareable artifact, steppable forward/backward.
• P3 — Edit a sequence: reorder, insert, remove steps.

Non-goals

• In-session graph shaping (expand/collapse) — covered by the sibling issue.
• Cross-deployment / access-controlled sharing.
• Short-URL services, private-view authentication.
• Mobile/touch interaction.

Acceptance

• A view exported on one machine and imported on another reproduces the visible set, edges, and positions pixel-accurately against the same underlying data.
• An import where some references no longer resolve still renders the resolvable subset and reports the missing references.
• A sequence of 5+ views replays step-by-step with every step matching its authored view.