refactor(skills): make skills portable across users/locations via workspace-relative paths + env var overrides

Changes:
- skills/lib.sh:
  - HOME_DIR default changed from $HOME to <workspace_root> (workspace self-sufficient)
  - Added CLAUDE_PROJECT_DIR / LOCAL_BIN env var pattern (default $HOME, overridable)
- skills/tmux-agent-orchestrate-monitor/scripts/reconcile.sh:
  - STATE_DIR moved from $HOME/.cache/... to <workspace>/.cache/tmux-agent-orchestrate-monitor
- skills/tmux-agent-orchestrate-create/scripts/create_session.sh:
  - WRAPPER uses $LOCAL_BIN env var (default $HOME/.local/bin)
- 6 SKILL.md: examples and explanations updated to mention env var override capability

User/portability contract:
- Workspace-internal data: .hermes/ + .cache/ (moves with workspace)
- User/system data: $HOME/* (overridable via CLAUDE_PROJECT_DIR, LOCAL_BIN)
- All env vars follow: ${VAR:-default} pattern with documented defaults

Verified on isolated server -L agy-homeport-test (kill-server after):
- syntax check PASS
- E2E: defaults resolve to workspace-relative paths
- E2E: env var override correctly changes paths
- 0 leftover direct $HOME references in code
- Global skill non-interference verified
- Main isolated server -L multi-agent-canary untouched

skills/tmux-agent-orchestrate-create/scripts/create_session.sh

@@ -95,7 +95,8 @@ if _tmux has-session -t "$SESSION_NAME" 2>/dev/null; then
 fi
 
 # tmux 세션 띄우기
-WRAPPER="$HOME/.local/bin/$SESSION_NAME"
+LOCAL_BIN="${LOCAL_BIN:-$HOME/.local/bin}"
+WRAPPER="$LOCAL_BIN/$SESSION_NAME"
 
 spawn() {
   case "$AGENT" in