feat: edit a finished match (names, commanders, partners)

[Jshewmaker]

What & why

Adds inline editing of a finished match from the Match Details screen. After a game is over, a user can correct what was recorded for each player:

• Player name
• Commander (primary)
• Partner commander

A pencil action in the app bar flips the screen into edit mode (app bar shows Save ✓ / Cancel ✕); tapping a commander opens a full-screen Scryfall search picker. Saving persists changes to the current user's saved copy of the match via the existing updateGameStats, and the change reflects back automatically through the live MatchHistoryBloc stream.

Spec: docs/superpowers/specs/2026-06-18-edit-match-details-design.md
Plan: docs/superpowers/plans/2026-06-18-edit-match-details.md

How it works

• MatchEditCubit — owns a draft List<Player> during the edit session; save() builds game.copyWith(players: draft) and calls updateGameStats(game:, playerId: currentUserId). Save-error keeps the draft; cancel restores.
• CommanderPickerCubit + CommanderPickerView — a lightweight, isolated full-screen picker that searches Scryfall and returns a Commander (primary or partner).
• Shared magicCardToCommander helper — extracted from the live-game flow so both flows use one mapping (removes duplication).
• EditablePlayerTile / MatchEditPlayersList / MatchDetailsAppBarActions — small, independently-tested widgets wired into both the phone and tablet views.

While editing, the Winner/Metadata cards are hidden and a single editable players list is shown — a deliberate refinement that avoids two competing editable controls for the winner.

Scope

• Editable: name, commander, partner. Not editable: winner, placement, who-went-first, duration, room id, date.
• Localized (en + es).
• Known limitation: edits write only the current user's copy (users/{uid}/matches/{gameId}), mirroring existing delete/ownership behavior. Other participants' synced copies are not updated — a candidate follow-up.

Testing

• flutter test — 24/24 passing.
• Unit tests for MatchEditCubit (draft mutation, save success capturing the merged game, save-error preserves draft, cancel restores) and CommanderPickerCubit (legendary filter, failure path).
• Widget tests for the picker (pop-value), EditablePlayerTile (all callbacks incl. partner add/change/remove), app-bar actions (edit↔save/cancel), and the players list (picker → draft update).
• flutter analyze lib/match_details introduces 0 new lints (8 pre-existing info-level lints predate this feature).

Optional follow-ups (non-blocking, from final review)

• Reset MatchEditCubit to viewing after the success snackbar (currently rests at sticky success; behavior correct today).
• Add a view-level integration test driving the full edit → save → read-only loop through MatchDetailsView.
• Track participant fan-out as a backlog item.

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