Printing tracking for owned copies and deck art, and an outdated-card-data notice

Owned copies can now be pinned to a printing + finish (nonfoil / foil /
etched), activating the long-dormant library_card_copies table as groups
of identical copies. library_cards.quantity_owned stays authoritative:
groups are a subset of it, and the rest are "unspecified". Tracking more
copies than are unspecified grows ownership to fit; lowering ownership
trims the most recently added groups first. Migration 0006 adds the
group quantity, a unique (card, printing, finish) index, and
deck_cards.preferred_scryfall_id.

A deck slot can show a chosen printing's art, both faces from that
printing, falling back to the default when the id no longer resolves.
It survives quantity/board changes and is kept by duplicate_deck.

UI: the click preview's info tile gets a Printings section when opened
from the Library or a deck (copy groups with steppers, "Add a
printing…", and "Shown in this deck" with Change…/Default), backed by a
printing picker grid. The picker takes Escape in the capture phase so
it closes without closing the preview under it.

Sync: CardEntry.printings (keyed "<scryfall_id>/<finish>") and
DeckCardEntry.printing. Cards now merge field by field with groups per
key, so a quantity edit and a printing added on another device both
survive; merged groups are clamped deterministically. A document is
written as version 2 only once it holds printing data, so older builds
and servers refuse it instead of dropping the data and syncing the loss.

Decklists: "(SET) NUM", optionally "*F*"/"*E*", round-trips through deck
and library export/import. Library export writes a line per group plus
one for unspecified copies.

reference.db printings gain lang and released_at for picker labels and
ordering. When the installed card data lacks any column this build's
reference schema has (found by diffing against the schema applied
in-memory, so no list to maintain), a notice under the top bar offers
Update card data (and Import card data… on phones); "Not now" is
remembered until something more goes missing.

docs/printing-tracking-design.md

@@ -1,6 +1,8 @@
 # Design: optional per-printing tracking
 
-Status: **not implemented** — design only, for a future session.
+Status: **implemented.** The as-built decisions are in
+[As built](#as-built) at the end, which takes precedence over the original
+design below wherever the two differ.
 
 ## Context
 
@@ -148,3 +150,42 @@ later is a compatible follow-up, not a redesign.
 `crates/mtgc-core/src/model.rs`, `src-tauri/src/commands.rs`, `src/api.ts`,
 `src/components.tsx`, `src/views/DeckView.tsx`, `src/views/LibraryBrowser.tsx`,
 `src/views/CardEntry.tsx`.
+
+## As built
+
+Where the implementation settled the open questions, or departed from the
+design above:
+
+- **Migration** is `0006_printings.sql` (0005 had gone to deck uuids). It adds
+  `library_card_copies.quantity`, a unique index on
+  `(library_card_id, scryfall_id, finish)`, and `deck_cards.preferred_scryfall_id`.
+  Everything lives in `crates/mtgc-core/src/printings.rs`.
+- **No `remove_copy(copy_id)`.** `set_library_copy(.., quantity)` with
+  `quantity <= 0` removes a group, mirroring `set_deck_card`. Row ids are local
+  and are rebuilt on every sync, so they would be a poor handle anyway.
+- **Quantity rules (open question 3).**
+  - *Grow:* setting a group above the unspecified remainder raises
+    `quantity_owned` to fit.
+  - *Clamp:* lowering `quantity_owned` below the tracked total trims the
+    highest-id (most recently added) groups first.
+  - Lowering a group never lowers `quantity_owned`; those copies become
+    unspecified.
+  - All of this is pinned by tests in `printings.rs`.
+- **Library thumbnails (open question 1)** always show the oracle default.
+  Only deck slots show a chosen printing.
+- **Decklists (open question 2)** round-trip in this first cut, as
+  `(SET) NUM`, optionally followed by `*F*` / `*E*`. See `decklist.rs`.
+- **UI.** There is no per-row button. A *Printings* section in the
+  click-preview info tile appears whenever the caller passes a
+  `PreviewContext`, and it opens a `PrintingPicker`. Both are in
+  `src/components.tsx`.
+- **Sync, which postdates this design.**
+  - `CardEntry.printings` is keyed `"<scryfall_id>/<finish>"`, and
+    `DeckCardEntry.printing` holds the chosen printing.
+  - Cards now merge field by field, and their groups merge per key, so edits
+    to one card from two devices both survive. A merge result is clamped by
+    trimming from the end of key order, which comes out the same on every
+    device.
+  - A document is written as version 2 only once it holds printing data, so
+    older builds refuse it rather than dropping the data and syncing the loss.
+- **Follow-up:** choosing a printing while entering cards on Add Cards.