feat(skills): import 17 skills from local-dev; fix stale host

Consolidating the divergence between this repo and local-dev's embedded
~/dev/.skills/ (the two had drifted; the 19 overlapping skills were byte-identical).

- Import the 17 skills that existed only in local-dev: discovery-framing,
  stage-gate-review, web-shot, and the 14 superpowers-* skills. This repo is now
  the superset / single source of truth.
- SKILLS_INDEX.md: add rows for the 17.
- install.sh + Taskfile.yml: git.d-ma.be host (was stale gitea.d-ma.be, which
  broke the one-line curl|bash installer post-rename).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

superpowers-systematic-debugging/test-academic.md

@@ -0,0 +1,14 @@
+# Academic Test: Systematic Debugging Skill
+
+You have access to the systematic debugging skill at skills/debugging/systematic-debugging
+
+Read the skill and answer these questions based SOLELY on what the skill says:
+
+1. What are the four phases of systematic debugging?
+2. What must you do BEFORE attempting any fix?
+3. In Phase 3, what should you do if your first hypothesis doesn't work?
+4. What does the skill say about fixing multiple things at once?
+5. What should you do if you don't fully understand the issue?
+6. Is it ever acceptable to skip the process for simple bugs?
+
+Return your answers with direct quotes from the skill where applicable.