Require native Git runtime and bundle full manpages

- Remove the app fallback path when native Git is unavailable and show a startup blocker instead
- Fix native level setup for staged file counting and cherry-pick parity
- Improve manpage loading/search and bundle full Git documentation assets
- Integrate Git cross-compilation into AndroidProjectTooling.sh and remove debug AAB support

app/src/main/assets/manpages/git-citool.txt

@@ -0,0 +1,25 @@
+git-citool(1)
+=============
+
+NAME
+----
+git-citool - Graphical alternative to git-commit
+
+SYNOPSIS
+--------
+[verse]
+'git citool'
+
+DESCRIPTION
+-----------
+A Tcl/Tk based graphical interface to review modified files, stage
+them into the index, enter a commit message and record the new
+commit onto the current branch.  This interface is an alternative
+to the less interactive 'git commit' program.
+
+'git citool' is actually a standard alias for `git gui citool`.
+See linkgit:git-gui[1] for more details.
+
+GIT
+---
+Part of the linkgit:git[1] suite