feat(desktop): let the user choose where Windows installs CoDev

CHANGELOG.md

@@ -18,14 +18,25 @@ file is the human-readable summary of what changed and why.
   its downloaded updates in `@opencode-aidesktop-updater` beside it. Both names
   came from an internal package id that was never meant to be read, by way of a
   packaging rule that uses it rather than the product name for a per-user
-  install. They are now `codev` and `codev-updater` (`codev-beta`/`codev-dev` on
+  install. The update cache is now `codev-updater` (`codev-beta`/`codev-dev` on
   those channels, which previously shared one folder with each other and with
-  the release build). Already-installed copies stay where they are and keep
+  the release build), and the app itself installs into `CoDev` — see the
+  installer change below, which lets you put it wherever you like instead.
+  Already-installed copies stay where they are and keep
   updating — the installer reuses the location it recorded — so this changes
   where a fresh install lands, not where an existing one lives; a machine that
   had downloaded an update leaves the old cache folder behind, which is safe to
   delete. Linux and macOS are unaffected: the `.deb` package name is already
   `codev`, and nothing on macOS is derived from this name.
+- **You can choose where the Windows installer puts CoDev** — it installed
+  itself wherever it liked and gave you no say: one screen, no questions, done.
+  It now asks two. First whether to install for everyone on the computer or
+  just for you — just for you stays the default, and it is the one that needs no
+  administrator approval. Then where to put it, offering the usual place with a
+  **Browse** button beside it, so a machine with a small `C:` drive or a policy
+  about where programs live is no longer stuck. Updates are unaffected: they
+  still install quietly in the background and never re-ask, because an update
+  reuses the location you picked.
 
 ### Updates