feat: default printer selection to a real printer instead of Auto-select

[szrudi]

Stacked under #39 (per-printer settings); no version bump — ships in the single v1.8.0 that #39 cuts. Merges before #39, which builds on it.

Why

The printer dropdown defaulted to an "Auto-select" entry — meaning no concrete printer was chosen and the server picked one only at print time. With per-printer settings (#39), that's backwards: on load you'd see app defaults (12 mm black/white) and only see a printer's saved tape/colors after manually picking it. (Found while testing #39 on the Pi.)

What

• Default the selection to a concrete printer in setAvailablePrinters: the first printer in the list — which is the first real USB printer when present (virtual printers are listed after). So a real printer is selected on load, and (once feat: persist per-printer label settings (tape size, colors) — closes #20 #39 lands) its saved settings apply immediately.
• Re-select the first printer if the chosen one vanishes (unplugged), so the selection is never stale.
• Remove the "Auto-select" dropdown entry.
• The server still accepts no printer_id and auto-selects the first available printer — that fallback is unchanged; the UI just always sends a concrete printer now.

Tests

Store: defaults to first printer, keeps a still-present selection, re-selects on vanish, clears when no printers. SettingsBar: lists printers without Auto-select, defaults to first, selecting updates the store. Frontend suite green (59); ARCHITECTURE.md updated.

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[Copilot]

Pull request overview

This PR updates the frontend’s multi-printer selection behavior so the UI defaults to a concrete printer (the first in the discovered list) rather than an “Auto-select” placeholder, aligning the UX with upcoming per-printer settings in #39.

Changes:

• Updated the Zustand store (setAvailablePrinters) to default settings.printerId to the first available printer and to re-select the first printer if the prior selection disappears.
• Removed the “Auto-select” option from the SettingsBar printer dropdown and adjusted selection handling accordingly.
• Updated docs and frontend tests to reflect the new default-selection behavior.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/ARCHITECTURE.md	Updates the architecture notes to describe the new concrete default printer selection behavior.
client/src/state/useLabelStore.ts	Implements default/repair logic for printerId when available printers are set.
client/src/state/useLabelStore.test.ts	Adds unit tests for the new setAvailablePrinters selection behavior.
client/src/components/SettingsBar.tsx	Removes the “Auto-select” option and updates the printer selector change handler.
client/src/components/SettingsBar.test.tsx	Updates UI tests to expect no “Auto-select” option and default-first selection behavior.

Comments suppressed due to low confidence (1)

client/src/components/SettingsBar.tsx:43

• Now that the "Auto-select" entry is removed, the can be rendered with value={settings.printerId || ""} that doesn't match any option when printerId is undefined (e.g. after importing a label file that has no printerId). This results in an invalid controlled value and can show a blank selection / React warnings. Consider deriving an effectivePrinterId that falls back to the first available printer and using it consistently for both the selected printer lookup and the value. const selectedPrinter = settings.printerId ? availablePrinters.find((p) => p.id === settings.printerId) : null; const selectedIsVirtual = selectedPrinter?.vendorProductId === "virtual"; 💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.