mod: Phase 1 - bring forward mod-exclusive files with ActivityManager migration

Brings ~55 mod-exclusive files to the upstream-based mod/master-resync branch:

Activities (migrated to new ActivityManager pattern):
- Clock/Time: SetTimeActivity, SetTimezoneOffsetActivity, NtpSyncActivity
- Dictionary: DictionaryDefinitionActivity, DictionarySuggestionsActivity,
  DictionaryWordSelectActivity, LookedUpWordsActivity
- Bookmark: EpubReaderBookmarkSelectionActivity
- Book management: BookManageMenuActivity, EndOfBookMenuActivity
- OPDS: OpdsServerListActivity, OpdsSettingsActivity
- Utility: DirectoryPickerActivity, NumericStepperActivity

Utilities (unchanged):
- BookManager, BookSettings, BookmarkStore, BootNtpSync
- Dictionary, LookupHistory, TimeSync, OpdsServerStore

Libraries: PlaceholderCover, TableData, ChapterXPathIndexer
Scripts: inject_mod_version, generate_book_icon, preview_placeholder_cover
Docs: KOReader sync XPath mapping

Migration changes:
- ActivityWithSubactivity -> Activity base class
- Callback constructors -> finish()/setResult() pattern
- enterNewActivity() -> startActivityForResult()
- Activity::RenderLock&& -> RenderLock&&

These files won't compile yet - they reference mod settings and I18n
strings that will be added in subsequent phases.

Made-with: Cursor

chat-summaries/2026-02-21_readme-mod-update.md

@@ -0,0 +1,28 @@
+# README.md Update for Mod Branch
+
+**Date:** 2026-02-21
+
+## Task
+
+Updated `README.md` to distinguish this mod fork from upstream CrossPoint Reader, documenting all mod-exclusive features, updated feature status, upstream PR ports, and upstream compatibility notes.
+
+## Changes Made
+
+**File:** `README.md`
+
+1. **Header/intro** — Renamed to "CrossPoint Reader (Mod)" with a link to the upstream repo and a summary of what the mod provides. Added blockquote linking to upstream.
+2. **Motivation** — Added a paragraph explaining the mod's purpose (faster iteration on features and fixes). Fixed "truely" typo.
+3. **Features & Usage checklist** — Updated to reflect current mod capabilities:
+   - Checked: image support (JPEG/PNG), table rendering, bookmarks, dictionary, book management, clock, letterbox fill, placeholder covers, screen rotation (4 orientations), end-of-book menu, silent pre-indexing
+   - Added sub-items: file extensions, expandable rows
+   - Still unchecked: user provided fonts, full UTF, EPUB picker with cover art
+4. **New section: "What This Mod Adds"** — Organized by category (Reading Enhancements, Home Screen & Navigation, Book Management, Reader Menu, Display & Rendering, Performance). Documents bookmarks, dictionary, tables, end-of-book menu, clock/NTP, adaptive home screen, file browser improvements, archive system, manage book menu, long-press actions, letterbox fill, landscape CCW, silent pre-indexing, placeholder covers, and 5 ported upstream performance PRs.
+5. **New section: "Upstream Compatibility"** — Documents what's missing from the mod (BmpViewer, Catalan translations), build differences (font/hyphenation omissions, version string), and links to `mod/prs/MERGED.md`.
+6. **Installing** — Replaced web flasher instructions with `pio run -e mod --target upload`. Noted `env:default` alternative.
+7. **Development** — Updated clone command to use `-b mod/master`. Added build environments table (`mod` vs `default`). Updated flash command.
+8. **Contributing** — Simplified to note this is a personal mod fork with a link to the upstream repo for contributions.
+
+## Follow-up Items
+
+- `USER_GUIDE.md` is out of date and does not document mod features (bookmarks, dictionary, clock, book management, etc.)
+- The data caching section in Internals could be expanded to mention mod-specific cache files (`bookmarks.bin`, `book_settings.bin`, `dictionary.cache`, image `.pxc` files)