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>

install.sh

@@ -2,7 +2,7 @@
 # install.sh — bootstrap installer for the skills library.
 #
 # Usage (one-liner, hosts without Task):
-#   curl -fsSL https://gitea.d-ma.be/mathias/skills/raw/branch/main/install.sh | bash
+#   curl -fsSL https://git.d-ma.be/mathias/skills/raw/branch/main/install.sh | bash
 #
 # Pinned to a specific tag:
 #   SKILLS_REF=v0.1.0 bash install.sh
@@ -13,7 +13,7 @@
 
 set -euo pipefail
 
-REPO_URL="${SKILLS_REPO_URL:-https://gitea.d-ma.be/mathias/skills.git}"
+REPO_URL="${SKILLS_REPO_URL:-https://git.d-ma.be/mathias/skills.git}"
 REF="${SKILLS_REF:-main}"
 CHECKOUT_DIR="${SKILLS_CHECKOUT_DIR:-$HOME/.local/share/skills}"
 CLAUDE_GLOBAL_DIR="${CLAUDE_SKILLS_DIR:-$HOME/.claude/skills}"