fix: throttle worker heartbeat noise and align sidecar state

[kbentonferguson]

Summary

• throttle worker heartbeat/lease renewal away from the hot poll_seconds=0.1 loop
• add explicit --heartbeat-seconds support while preserving non-default --poll-seconds as the compatibility fallback
• keep heartbeat cadence safely below lease expiry for short leases
• scope PUPPETMASTER_STATE_DIR around inline workers so adapter sidecars land under the owning store root
• add regression coverage for heartbeat cadence, short-lease margin, and inline state-dir restoration

Why

Puppetmaster workers were renewing leases and emitting heartbeat/save events every 0.1s, producing thousands of events for ordinary runs and making logs/status debugging noisy. Slowing the default heartbeat path cuts that event churn while preserving lease safety and existing callers that tuned --poll-seconds.

Inline worker mode also did not export the resolved store root through PUPPETMASTER_STATE_DIR, so adapter sidecar logs could be written under the wrong project state dir when the parent environment pointed elsewhere.

Tests

• python3 -m pytest tests/test_puppetmaster.py -q -k 'heartbeat or inline_workers_scope_state_dir'
• env -u CODEX_COMMAND -u CODEX_CI -u CODEX_HOME -u CODEX_PATH -u CODEX_THREAD_ID python3 -m pytest tests/test_puppetmaster.py -q
• git diff --check
• Puppetmaster confidence review:
  • tests review job_391b13303b3b: no blocking issue
  • inline state-dir review job_08b8c258fd9e: no blocking issue
  • heartbeat review job_d5fb9427fc66: surfaced compatibility/short-lease findings addressed in this PR