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-delete/SKILL.md

@@ -120,8 +120,8 @@ print(f'OK: terminated at {s[\"terminated_at\"]}')
 print(f'  preserved: pane.pid={s[\"pane\"][\"pid\"]}, cmd={s[\"pane\"][\"cmd\"]}, cwd={s[\"pane\"][\"cwd\"]}')
 "
 
-# 3. (if --purge-conversation) disk artifacts gone
-[ -f "$HOME/.claude/projects/<projkey>/<uuid>.jsonl" ] && echo "WARN: jsonl still exists" || echo "OK: jsonl purged"
+# 3. (if --purge-conversation) disk artifacts gone (CLAUDE_PROJECT_DIR env var overrides default $HOME/.claude/projects)
+[ -f "${CLAUDE_PROJECT_DIR:-$HOME/.claude/projects}/<projkey>/<uuid>.jsonl" ] && echo "WARN: jsonl still exists" || echo "OK: jsonl purged"
 ```
 
 ## When NOT to use this skill