fix(commands): rename NFR references to success criteria in analyze and clarify (#1935)

* fix(commands): rename NFR references to success criteria in analyze and clarify

* fix(analyze): align Success Criteria description and inventory keys with spec template

- Reword "non-functional targets" to "measurable outcomes" to match the spec template's broader scope (performance, user success, business impact)
- Use explicit FR-/SC- identifiers as primary stable keys in the requirements inventory instead of derived slugs alone

templates/commands/clarify.md

@@ -145,7 +145,7 @@ Execution steps:
        - Functional ambiguity → Update or add a bullet in Functional Requirements.
        - User interaction / actor distinction → Update User Stories or Actors subsection (if present) with clarified role, constraint, or scenario.
        - Data shape / entities → Update Data Model (add fields, types, relationships) preserving ordering; note added constraints succinctly.
-       - Non-functional constraint → Add/modify measurable criteria in Non-Functional / Quality Attributes section (convert vague adjective to metric or explicit target).
+       - Non-functional constraint → Add/modify measurable criteria in Success Criteria > Measurable Outcomes (convert vague adjective to metric or explicit target).
        - Edge case / negative flow → Add a new bullet under Edge Cases / Error Handling (or create such subsection if template provides placeholder for it).
        - Terminology conflict → Normalize term across spec; retain original only if necessary by adding `(formerly referred to as "X")` once.
     - If the clarification invalidates an earlier ambiguous statement, replace that statement instead of duplicating; leave no obsolete contradictory text.