Feat/multi select

[NateEaton]

Summary

Adds full multi-select mode to the bookmark list and reworks the list top app bar into an overflow menu. Covers selection, batch favorite/archive/delete, batch add-labels, and the bar consolidation — the complete multi-select scope.

What's included

Multi-select mode

• Enter selection mode from the top-bar overflow; tap cards to select. Selection-mode bar shows X / count / Archive / Favorite / Overflow; the overflow holds Delete, Add labels, and Select All / Deselect All.
• Select All toggles selection across the full filtered list.
• Single context-aware action icons. Favorite and Archive each show one icon reflecting what the tap will do across the whole selection: if every selected item is already favorited/archived the icon is the "remove" variant (and the tap removes for all); otherwise it's the "add" variant. Writes skip no-op items.
• Favorite, Archive, and Add labels keep the selection active so several actions can run in a row; selection mode auto-exits when an action leaves nothing selected.
• In selection mode, each card's favorite/archive icons stay visible but dimmed (~38% alpha) as non-interactive state indicators.

Batch add labels

• Additive "Add labels" applies one or more labels (union per bookmark) to the whole selection via the existing label picker and UPDATE_LABELS sync path. Bookmarks already carrying all chosen labels are skipped. Snackbar confirms with an Undo that restores prior labels. (Batch removing labels is out of scope.)

Batch delete + Undo

• Delete stages items optimistically (no DB write), exits selection mode, and surfaces a Snackbar with Undo.
• A single Snackbar + Undo is the confirmation surface for all multi-select changes — delete, favorite/archive, and add-labels. Undo reverts only the items actually changed (changedIds); delete uses Indefinite duration, the reversible actions use Long.
• Repository deleteBookmarks(ids) performs one transaction (soft-delete + clear stale pending actions + one DELETE pending action per id) and schedules sync once. Batch-pending delete state is kept separate from single-item delete so confirm/cancel is atomic.

Top app bar overflow refactor

• Normal mode: Layout / Sort / always-present MoreVert overflow (Filter + Select bookmarks).
• Label mode: same bar shape; overflow holds Rename label / Delete label / divider / Select bookmarks. Eliminates the previous "multi-select icon to the right of the overflow" gap.

Docs / conventions

• New specs list-top-app-bar-overflow-spec.md and list-multi-select-phase-4-spec.md; list-multi-select-actions-spec.md updated (Snackbar+Undo confirmation, no settings toggle). User guide (your-bookmarks.md, organizing.md) updated.
• Snackbar copy uses flat strings across all 10 locales (no <plurals>), per project convention.
• CLAUDE.md: added "copyable deliverables as raw markdown" instruction (unrelated housekeeping carried on this branch).

Out of scope

• A settings-level confirmation toggle (dropped — the Snackbar+Undo supersedes it).
• Batch removing labels.

Test plan

• ./gradlew :app:assembleDebugAll
• ./gradlew :app:testDebugUnitTestAll
• ./gradlew :app:lintDebugAll
• On-device (Pixel 9): select/deselect, Select All, batch favorite/archive (context-aware icon + keep-selection + auto-exit), dimmed card icons, batch add-labels + Undo, batch delete + Undo, normal- and label-mode overflow contents.