…transitions

Adds the listener that writes a chain event for every transition
through the OperationalStateHolder. PM-verified vocabulary against
foundation/0159_kora_r41_operational_state_event_vocabulary.sql on
isokron-prod (2026-05-21):

  * ALWAYS emit ``kora.operational_state.transitioned`` — single
    generic edge event per substrate-team design. Payload carries
    from/to primary_state, new claim_permission, sorted
    degradation_reasons, and trigger.
  * ADDITIONALLY emit when a per-trigger literal exists:
      - (BOOTING → READY, "all §9.2 gates pass") → kora.boot.ready
      - (BOOTING → STOPPED, "invariant gate failure …") →
        kora.boot.failed
      - (any → PAUSED, trigger contains "cost 100%") →
        kora.paused.cost_limit
  * Operator-pause and substrate-pause: only the generic event.
    Per-trigger literals can land in a follow-on substrate vocab
    migration if cockpit needs the signal.

Fail-LOUD: preflight failures (missing provider / connection /
workspace_id) and substrate-side raises both surface as
OperationalStateEmitError. The state-machine listener-error
handler logs but doesn't roll back — listeners are observability,
not policy — so a broken emit is loudly logged but the state
machine keeps moving.

agent/operational_state_emit.py exposes:
  - GENERIC_TRANSITION_EVENT, BOOT_READY_EVENT, BOOT_FAILED_EVENT,
    PAUSED_COST_LIMIT_EVENT — constants matched against
    foundation/0159
  - emit_state_transition(provider, from, to, trigger) — async
    callable, fail-LOUD
  - make_emit_listener(provider) — factory returning a
    StateTransitionListener; ST3 wires this into the holder at
    provider init

Tests (tests/test_operational_state_emit.py): 16 cases covering
payload shape, per-trigger literal selection (incl. lenient
substring match for varied caller wording), the BOOTING → STOPPED
disambiguation (invariant-failure vs STOP-KORA L4/L5), fail-LOUD
preflight (None provider, missing connection, workspace_id raise
or empty), generic-plus-extra dual-emit, substrate-failure
propagation, and the make_emit_listener factory.

Builds on ST1 (#32). ST3 will land the wire-in.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>