electron/main.cjs is the worst god file in the desktop app (~7.6k lines, 93 IPC
handlers across unrelated domains). Begin peeling cohesive handler clusters into
sibling modules — the established main.cjs pattern.
First cluster: the 19 git/worktree/review IPC handlers (all thin delegators to
the existing git-*-ops modules) move into a new electron/git-ipc.cjs exposing
registerGitIpc({ ipcMain, resolveGitBinary, resolveGhBinary }). The git/gh
binary resolvers stay in main.cjs (Windows PATH discovery) and are injected, so
the new module is pure. Channel names are unchanged, so preload/renderer are
unaffected.
Adds electron/git-ipc.test.cjs (wired into test:desktop:platforms) asserting
the full channel surface and resolver delegation. main.cjs: 7,617 -> 7,530.
