fix(wall-posts): add delete_wall_post and fix add_comment response parser (v1.3.1)

- Fix add_comment response parser: corrected to a00.r.r.comment.commentId structure
- Fix add_comment error handling: return errors directly instead of warnings
- Add delete_wall_post: permanently delete wall posts via metadelete endpoint
- Add delete_wall_post to README.md Wall & Activities section
- Update SPEC.md with correct walladdComment response structure
- Update SPEC.md metadelete to include wall posts as supported type
- Update CHANGELOG.md with v1.3.1 bugfixes and additions
- Version bumped to 1.3.1 in pyproject.toml

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

README.md

@@ -2,7 +2,7 @@
 
 MCP server for [Family Wall](https://www.familywall.com) — manage your family's circles, lists, tasks, recipes, and meal plan directly from Claude.
 
-## Tools (v1.3.0)
+## Tools (v1.3.1)
 
 ### Wall & Activities
 
@@ -12,6 +12,7 @@ MCP server for [Family Wall](https://www.familywall.com) — manage your family'
 | `create_wall_post` 🔒 | Create a new status post on the wall |
 | `add_comment` 🔒 | Add a comment to a post |
 | `like_post` 🔒 | Like or unlike a wall post/activity |
+| `delete_wall_post` 🔒 | Permanently delete a wall post |
 
 ### Circles & Members