fix(templater): ref with for loops

[hans-d]

Loop variables are now available to ref: inside looped task calls, matching the behavior of template substitutions.

Fixes #2505

• Fix loop ref resolution: Added ResolveRefWithExtra and wired ReplaceVarWithExtra to it so variable references (ref:) now receive the per-iteration extra map (loop variables and aliases). ResolveRef now delegates to the new helper to keep behavior consistent for non-loop callers.
• Added unit test and testdata