FE-502, H-6330: Improve SDCPN file import/export and file save/open behaviour

[kube]

🌟 What is the purpose of this PR?

Fixes the bug where importing an SDCPN file exported without visual info breaks the editor. Also improves the file format with Zod validation and a versioned envelope. Additionally improves the File menu save/open behaviour.

🔗 Related links

• FE-502: Importing back an export without visual info breaks the editor (internal)
• H-6330: Improve Petrinaut file save/open behaviour (internal)

🔍 What does this change?

• Moves file format code into src/file-format/ (export-sdcpn, import-sdcpn, remove-visual-info)
• Removes old-format (before November 2025)
• Replaces manual type guards with Zod schemas for import validation, matching the pattern used for clipboard in clipboard/types.ts
• Adds versioned file format envelope (version, meta.generator) to exported files
• Fixes layout on import: when nodes are missing x/y, runs ELK layout before calling createNewNet (avoids a stale closure bug where positions were applied to the wrong net)
• Adds onlyMissingPositions option to calculateGraphLayout for partial re-layout of imported nodes
• Adds ImportErrorDialog showing Zod validation errors with a "Create empty net" fallback
• Caps Open submenu height so it doesn't go off-screen with many files (scrollable, max 400px / viewport-relative)
• Sorts Open menu by most recently updated net first
• Cleans up empty nets — empty, unmodified nets are removed from storage when the user switches away or creates a new net
• Updates lastUpdated on mutation so the sort order reflects actual edit activity

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• does not modify any publishable blocks or libraries, or modifications do not need publishing

📜 Does this require a change to the docs?

The changes in this PR:

• are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

❓ How to test this?

1. Export a net as "JSON without visual info"
2. Import the exported file back
3. Confirm all nodes are laid out by ELK (not stacked at origin)
4. Import a malformed JSON file and confirm the error dialog appears
5. Create several nets via File → New, verify empty ones are cleaned up when switching away
6. Open the File → Open menu with many nets, confirm it scrolls instead of going off-screen
7. Edit a net, then check that it appears at the top of the Open menu

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Project	Deployment	Actions	Updated (UTC)
hash	Ready	Preview, Comment	Mar 17, 2026 11:36pm
petrinaut	Ready	Preview	Mar 17, 2026 11:36pm

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
hashdotdesign	Ignored	Preview	Mar 17, 2026 11:36pm
hashdotdesign-tokens	Ignored	Preview	Mar 17, 2026 11:36pm

[kube]

• FE-502, H-6330: Improve SDCPN file import/export and file save/open behaviour #8536 👈 (View in Graphite)
• FE-504: Add Copy, Paste and Select All to Petrinaut editor #8533
• FE-512: Create FilterableListSubView with keyboard navigation and search #8532
• H-6324: Migrate petrinaut to oxlint and verify React Compiler #8539 : 4 other dependent PRs (#8537 , #8541 , #8549 and 1 other)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[cursor]

PR Summary

Medium Risk
Moderate risk: changes SDCPN file import/export format/validation and editor import flow (including auto-layout), which could break backward compatibility or edge-case files if schemas/layout assumptions are wrong.

Overview
Improves Petrinaut SDCPN import/export by introducing a versioned file envelope (version, meta.generator) on export and a new Zod-validated import pipeline (parseSDCPNFile) that supports both versioned and legacy files, with clearer error reporting.

Fixes imports of files missing visual info by defaulting absent arrays/visual fields (including missing x/y) and, when positions are missing, running ELK layout before createNewNet to avoid loading a broken/stacked graph. Import failures now surface via a new ImportErrorDialog with a “Create empty net” fallback.

Improves net switching UX by adding lastUpdated to MinimalNetMetadata/persisted nets, showing relative timestamps in the Open submenu, making submenus scrollable, sorting nets by most-recently-updated, updating lastUpdated on edits, and cleaning up empty unmodified local nets when switching/creating new nets. Hash frontend now includes lastUpdated from entity metadata when listing persisted nets.

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[augmentcode]

🤖 Augment PR Summary

Summary: This PR refactors Petrinaut’s SDCPN JSON import/export to be versioned and Zod-validated, and improves the import experience when node positions are missing.

Changes:

• Moved SDCPN file I/O helpers into src/file-format/ (export, import, remove-visual-info, old-format converters).
• Introduced a v1 on-disk JSON envelope with version and meta.generator metadata on export.
• Added Zod schemas for both the versioned format and a legacy (unversioned) format, using defaults for optional sections.
• Reworked import to return a structured result (success/error) and to detect missing x/y coordinates.
• On import, fills missing coordinates and (when needed) runs ELK layout before calling createNewNet to avoid stale-closure issues.
• Extended calculateGraphLayout with an onlyMissingPositions option to support partial re-layout.
• Added an ImportErrorDialog to display validation/read errors with a “Create empty net” fallback.

Technical Notes: The new importer prefers the versioned schema first, falls back to the legacy schema, and uses user settings (compact vs classic node dimensions) when computing ELK layout.

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[augmentcode]

Review completed. 3 suggestions posted.

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[augmentcode]

Review completed. 4 suggestions posted.

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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