chore: archive stale notes, delete to-issues/to-prd skills, clean install.sh

- docs/notes/archive/: move ai-ethics-security-principles.md and
  team-self-organisation-sprint-brief.md (superseded/out of scope)
- plugins/bin/skills/: delete to-issues and to-prd (stale mattpocock
  adoptions with no Gitea target; replacement tracked separately)
- scripts/install.sh: remove dead .agents/skills/ deployment block and
  provider skill adapter symlink code; neither path exists in this repo

Closes items 8, 9, 10 of issue #15.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/install.sh

@@ -5,14 +5,6 @@ REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
 # shellcheck source=scripts/deploy-manifest.sh
 source "$REPO_ROOT/scripts/deploy-manifest.sh"
 
-# Collect provider skill adapters from all provider-manifest.sh files
-SKILL_ADAPTERS=()
-for provider_manifest in "$REPO_ROOT"/providers/*/provider-manifest.sh; do
-  [[ -f "$provider_manifest" ]] || continue
-  # shellcheck source=/dev/null
-  source "$provider_manifest"
-done
-
 echo "Installing from $REPO_ROOT..."
 
 for entry in "${DEPLOY_FILES[@]}"; do
@@ -35,33 +27,6 @@ for entry in "${DEPLOY_DIRS[@]}"; do
   cp -r "$REPO_ROOT/${entry%%:*}/." "$dest/"
 done
 
-# Deploy skills to canonical location — merge per-skill, never wipe the parent
-# Skipped when source does not exist (marketplace architecture: skills installed via plugin)
-skills_dest="$HOME/$DEPLOY_SKILLS_SRC"
-skills_deployed=()
-if [[ -d "$REPO_ROOT/$DEPLOY_SKILLS_SRC" ]]; then
-  mkdir -p "$skills_dest"
-  for skill_dir in "$REPO_ROOT/$DEPLOY_SKILLS_SRC"/*/; do
-    [[ -d "$skill_dir" ]] || continue
-    skill_name="$(basename "$skill_dir")"
-    rm -rf "${skills_dest:?}/${skill_name:?}"
-    cp -r "$skill_dir" "$skills_dest/$skill_name"
-    skills_deployed+=("$skill_name")
-  done
-fi
-
-# Create provider skill adapters as symlinks to the canonical skills location
-for adapter in "${SKILL_ADAPTERS[@]}"; do
-  target="$HOME/$adapter"
-  if [ -L "$target" ]; then
-    ln -sfn "$skills_dest" "$target"
-  elif [ -d "$target" ]; then
-    echo "Warning: $target exists as a real directory — remove it and re-run install to create the skill adapter symlink."
-  else
-    ln -s "$skills_dest" "$target"
-  fi
-done
-
 # Install git hooks into the current repo checkout
 HOOKS_SRC="$REPO_ROOT/scripts/git-hooks"
 if [[ -d "$HOOKS_SRC" ]]; then
@@ -82,9 +47,3 @@ done
 for entry in "${DEPLOY_DIRS[@]}"; do
   echo "  ~/${entry##*:}/"
 done
-if [[ ${#skills_deployed[@]} -gt 0 ]]; then
-  echo "  ~/$DEPLOY_SKILLS_SRC/ (skills: ${skills_deployed[*]})"
-fi
-for adapter in "${SKILL_ADAPTERS[@]}"; do
-  echo "  ~/$adapter -> ~/$DEPLOY_SKILLS_SRC (symlink)"
-done