✨ Replace history for image-based reading

[qinghon]

Closes #1378

Description

Summary of changes

Fixed the issue where navigating to a different page inside the reader (image / PDF / CBZ/CBR) — e.g. via the "Go to page" input or switching reading mode — pushed a new history entry instead of replacing the current one. As a result, the browser Back button stepped through every visited page one-by-one rather than exiting the reader.

The fix makes these internal reader navigations replace the current history entry instead of adding to it:

• packages/browser/src/scenes/book/reader/BookReaderScene.tsx — the auto-navigation to the reader route (EPUB → reader, PDF → reader, and page-clamp redirects) now uses { replace: true }
• packages/browser/src/components/readers/imageBased/ImageBasedReader.tsx — "Go to page" navigation now replaces the current entry
• packages/browser/src/components/readers/imageBased/container/ReaderSettings.tsx — changing the reading mode (which rewrites the ?page= search param) now replaces the current entry
• packages/browser/src/components/readers/imageBased/continuous/ContinuousScrollReader.tsx — clearing the ?page= param when switching to continuous scroll now replaces the current entry

Reasoning

Switching pages is a transient in-reader action, not a meaningful "back" destination. By replacing the history entry, the Back button takes you back to where you were before opening the reader, which is the expected behavior.

Additional context

Affects the web reader only (packages/browser). No state/logic changes — purely the navigation mode of existing navigate() / setSearch() calls.

Screenshots

(Non-visual behavioral change — no screenshots. You can verify by opening a multi-page PDF/CBZ, jumping between pages, then pressing the browser Back button; it should leave the reader in one press instead of stepping back through each page.)

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[aaronleopold]

thank you!