launcher: image auto-resolution, --user in-place config persistence, --debug SPEC, install/uninstall image handling

run_oci.sh:
- Resolve the installed coderai image when none is given (single -> use it,
  several -> menu); no longer hardcodes a possibly-wrong tag.
- --debug accepts SPEC as the next token (not just --debug=SPEC) and won't
  swallow an image-looking arg, fixing "image: <debug spec>" mishaps.
- --local puts the runtime dir under ~/.config/coderai-runtime (override
  --data-dir).
- New --user[=UID[:GID]]: run as that user and switch a config dir to an
  IN-PLACE mount so the app's config edits persist (owned by you). Without
  --user, --local/--config-dir stay a throwaway copy. Banner shows user.

Non-destructive config persistence (no startup rewrite):
- codai/cli.py: new --host/--port that override config.server in memory only.
- codai/main.py: apply those overrides right after config load (never written
  to config.json).
- coderai-oci: pass --host/--port to the server and stop rewriting an existing
  config.json (only create one on true first run) — so an in-place-mounted
  config dir is never modified at startup.

install.sh / uninstall.sh:
- install: after loading, offer to remove OTHER coderai images (default no);
  no auto-launch.
- uninstall: resolve the installed coderai image(s) to remove (single ->
  confirm, several -> menu / all / none) instead of a hardcoded tag.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>