fix(compiler): CLI vars have highest priority in scoped mode

In scoped mode, CLI vars (e.g., `task foo VAR=value`) now correctly
override task-level vars. This is achieved by:

1. Adding a `CLIVars` field to the Compiler struct
2. Storing CLI globals in this field after parsing
3. Applying CLI vars last in scoped mode to ensure they override everything

The order of variable resolution in scoped mode is now:
1. OS env → {{.env.XXX}}
2. Root taskfile env → {{.env.XXX}}
3. Root taskfile vars → {{.VAR}}
4. Include taskfile env/vars (if applicable)
5. IncludeVars (vars passed via includes: section)
6. Task-level vars
7. CLI vars (highest priority)

Legacy mode behavior is unchanged.

testdata/scoped_taskfiles/Taskfile.yml

@@ -36,3 +36,9 @@ tasks:
       # In scoped mode, {{.ROOT_ENV}} should be empty (env not at root)
       # In legacy mode, {{.ROOT_ENV}} would have the value
       - echo "ROOT_ENV_AT_ROOT={{.ROOT_ENV}}"
+
+  prout:
+    vars:
+      LOL: prout_from_root
+    cmds:
+      - echo "{{.LOL}}"