feat(cli): let ktx setup --agents choose an install directory (#298)

Split the fused directory concept into projectDir (what the agent config
references) and installRoot (where project-scoped files are written), so
users can install .claude/, .mcp.json, skills, and rules where they open
their agent instead of only in the ktx project directory.

- Add --install-dir <path> (resolved against cwd, created if missing,
  mutually exclusive with --global/--local, rejected for claude-desktop).
- Add an interactive directory menu: ktx project dir / Current directory
  (hidden when it equals the project dir) / Custom directory… / Global
  scope (shown only when every target supports it).
- Expand a leading ~ in typed/quoted paths so the ~/… menu hints round-trip.
- Record installRoot in the install manifest and merge key; thread it
  through file planning, MCP config paths, summaries, and next actions.
- Refresh uv.lock to 0.12.0 for the editable ktx-sl and ktx-daemon packages.

uv.lock

@@ -466,7 +466,7 @@ wheels = [
 
 [[package]]
 name = "ktx-daemon"
-version = "0.11.0"
+version = "0.12.0"
 source = { editable = "python/ktx-daemon" }
 dependencies = [
     { name = "fastapi" },
@@ -523,7 +523,7 @@ dev = [
 
 [[package]]
 name = "ktx-sl"
-version = "0.11.0"
+version = "0.12.0"
 source = { editable = "python/ktx-sl" }
 dependencies = [
     { name = "pydantic" },