[everpcpc]

What

Renames the page "isolation" vocabulary to solo throughout the app, matching what the feature actually does: a solo page is not paired with its neighbor in dual-page mode.

UI strings (English source):

• Isolate → Show Solo
• Cancel Isolation → Cancel Solo
• Isolate Page %d → Show Page %d Solo
• Isolate Cover Page → Solo Cover Page (the dual-page cover preference, DIVINA and PDF)
• The image context-menu settings description now reads "sharing or showing a page solo"

All 10 supported languages re-translated; zh-Hans/zh-Hant/ja/ko keep their existing (already correct) "show alone" wording. The revert action is Cancel Solo rather than a "show paired" phrasing because un-soloing does not guarantee the page pairs (its neighbor may also be solo, or dual-page mode may be off).

Code symbols renamed end to end: ReaderPageIsolationActions → ReaderPageSoloActions, toggleIsolatePage → toggleSoloPage, isPageIsolated/isCurrentPageIsolated → isPageSolo/isCurrentPageSolo, supportsPageIsolationActions → supportsPageSoloActions, canIsolatePageFromCurrentPresentation → canSoloPageFromCurrentPresentation, isolateCoverPage/pdfIsolateCoverPage → soloCoverPage/pdfSoloCoverPage, fetchIsolatePages/updateIsolatePages → fetchSoloPages/updateSoloPages, and the file ReaderPageSoloActions.swift.

Persisted names intentionally kept, with a note at each site:

• GRDB column isolate_pages_raw — renaming it would buy nothing but a migration.
• UserDefaults keys isolateCoverPage / pdfIsolateCoverPage — renaming them would silently reset existing users' preferences.

Why

"Isolate" reads as exclusion or export (quarantine the page, take it out of the book), which is misleading — the page stays right where it is, it just shows alone instead of paired. The misleading source string already propagated: de/es/it/ru translated it as quarantine vocabulary, while zh/ja/ko/fr were translated by actual behavior ("show alone"). Aligning the source string with the behavior fixes both halves.

Validation

• make format
• make build — iOS, macOS, tvOS all built successfully
• make localize + ./misc/translate.py list → no missing translations; the five replaced keys were removed with translate.py remove
• No behavior change; verified by inspection that persisted keys/columns are untouched and every former isolate symbol/string reference was renamed (repo-wide grep), including the title-compare sites and the macOS menu selectors.

Includes make bump to build 642.

Also fixes the root cause of recurring extractionState: stale churn on "Enter Offline Mode": ServerView and ServerCardView built their label with a ternary inside String(localized:), which the strings extractor cannot resolve statically. Both call sites now hoist the branch outside the localized call so every key is a static literal — verified that make localize no longer flags the key.