feat(install): add Mistral Vibe wiring target (parity with local-dev)

Ports the Vibe wiring from local-dev's wire-skills.sh so this repo's installer
covers all four harnesses. Vibe uses a flat layout — ~/.vibe/skills/<name>.md
symlinked to the skill's SKILL.md file (not the directory, unlike Claude/Crush/
Antigravity). Added to both `task install` and install.sh, idempotent.

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

install.sh

@@ -19,6 +19,7 @@ CHECKOUT_DIR="${SKILLS_CHECKOUT_DIR:-$HOME/.local/share/skills}"
 CLAUDE_GLOBAL_DIR="${CLAUDE_SKILLS_DIR:-$HOME/.claude/skills}"
 CRUSH_DIR="${CRUSH_SKILLS_DIR:-$HOME/.config/crush/skills}"
 ANTIGRAVITY_DIR="${ANTIGRAVITY_SKILLS_DIR:-$HOME/.gemini/antigravity/skills}"
+VIBE_SKILLS_DIR="${VIBE_SKILLS_DIR:-$HOME/.vibe/skills}"
 
 log() { printf '[skills] %s\n' "$*"; }
 
@@ -112,12 +113,35 @@ wire_claude_repo() {
   done < <(list_skills)
 }
 
+wire_vibe() {
+  # Mistral Vibe reads a flat ~/.vibe/skills/<name>.md — link the SKILL.md
+  # file directly (not the skill directory, as the other harnesses do).
+  mkdir -p "$VIBE_SKILLS_DIR"
+  while IFS= read -r skill; do
+    [ -n "$skill" ] || continue
+    local target="$CHECKOUT_DIR/$skill/SKILL.md"
+    [ -f "$target" ] || continue
+    local link="$VIBE_SKILLS_DIR/$skill.md"
+    if [ -L "$link" ] || [ -e "$link" ]; then
+      local current
+      current=$(readlink "$link" 2>/dev/null || true)
+      if [ "$current" = "$target" ]; then
+        continue
+      fi
+      rm -rf "$link"
+    fi
+    ln -s "$target" "$link"
+    log "linked $link → $target"
+  done < <(list_skills)
+}
+
 main() {
   ensure_checkout
   wire_claude_global
   wire_claude_repo
   wire_crush
   wire_antigravity
+  wire_vibe
   log "done — $(list_skills | wc -l | tr -d ' ') skill(s) wired at ref=$REF"
 }