Add Deprecation Path to spec template and instructions

- Add Deprecation Path as a recognized section in specs.instructions.md
- Add Deprecation Path section to spec-template.md with comment directive
- Fix casing: 'Future considerations' -> 'Future Considerations' in template

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: denelon

.github/instructions/specs.instructions.md

@@ -61,8 +61,9 @@ Follow the template structure in order:
 5. **UI/UX Design** — What the user sees. Include terminal output examples showing exact formatting.
 6. **Capabilities** — Subsections for Accessibility, Security, Reliability, Compatibility, and Performance/Power/Efficiency.
 7. **Potential Issues** — Known risks, trade-offs, and concerns.
-8. **Future Considerations** — What this enables for later. Use this for ideas that are explicitly out of scope.
-9. **Resources** — Links to related issues, documentation, schema files, and external references.
+8. **Deprecation Path** (when applicable) — If the spec replaces an existing field or feature, include a phased deprecation table.
+9. **Future Considerations** — What this enables for later. Use this for ideas that are explicitly out of scope.
+10. **Resources** — Links to related issues, documentation, schema files, and external references.
 
 ## Content Guidelines
 

doc/specs/spec-template.md

@@ -53,7 +53,11 @@ issue id: <github issue id>
 
 [comment]: # What are some of the things that might cause problems with the fixes/features proposed? Consider how the user might be negatively impacted.
 
-## Future considerations
+## Deprecation Path
+
+[comment]: # If this spec replaces an existing field or feature, outline the phased deprecation plan. If not applicable, state that explicitly.
+
+## Future Considerations
 
 [comment]: # What are some of the things that the fixes/features might unlock in the future? Does the implementation of this spec enable scenarios?