…t zero LLM cost

Per Council R3 Lock R3-4 item #3. Enables routine status queries
("burn this week?", "any alerts?", "what's open?") to be answered
at $0 LLM cost — engine reads the pre-computed snapshot instead
of tool-calling. Foundational infrastructure for probe-audit work
+ reasoning-engine routing-layer short-circuit (separate bucket
KR-SNAPSHOT-INTO-ROUTING wires the consumer side).

# New module: kora_cli/snapshot/

  * ``state_snapshot.py`` — pure projection from live read
    accessors (operational_state_holder + cost_state_holder +
    alerts aggregator + heartbeat probe snapshots). Per-source
    collectors are independently fail-soft: a single source
    failure degrades only that section to ``"unknown"`` (or null
    where shape requires).
  * ``__init__.py`` — public surface (compute / write / read /
    is_fresh / snapshot_path / run_snapshot_cycle / SCHEMA_VERSION)
    + ``get_snapshot_for_routing()`` convenience the future
    reasoning-engine routing-layer bucket consumes.

Snapshot file: ``${KORA_HOME}/cache/daemon_snapshot.json`` (atomic
write via existing ``utils.atomic_replace``, the same pattern
cron/jobs.py uses for jobs.json).

# Schema v1 — populated vs degraded

| Section | Field | Source | v1 disposition |
|---|---|---|---|
| operational_state | primary | get_holder().current.primary_state | ✅ populated |
| operational_state | paused | derived from primary | ✅ populated |
| operational_state | pause_reason | degradation_reasons[0].value when paused | ✅ populated (null when empty set) |
| alerts | active_count | len(compute_active_alerts()) | ✅ populated |
| alerts | by_severity | rollup of alerts | ✅ populated |
| alerts | by_category | rollup of alerts | ✅ populated |
| cost_ladder | current_tier | get_cost_holder().active_rung().name | ✅ populated |
| cost_ladder | monthly_budget_pct_used | get_cost_holder().current_pct_used() * 100 | ✅ populated |
| cost_ladder | model_default | dynamic per-call downshift (no holder field) | ⚠️ "unknown" v1 |
| service_health | {vercel,sentry,doppler,supabase,fly} | current_service_snapshots()[name].status | ✅ populated (per-probe degrade to "unknown" if absent) |
| tasks | open_count, in_progress_count | substrate Sea_Tickets read | ⏸️ "unknown" v1 (deferred per spec §4 — MCP call at 5-min cadence flagged ASK; follow-on bucket can wire cached substrate read) |

# Listener wiring

New ``kora_cli/listeners/snapshot_listener.py`` registers via
``register_daemon_listener("snapshot", factory)`` + the periodic
task ``snapshot.compute`` via ``register_periodic_task`` from the
heartbeat scheduler. Cadence default 300s (5 min);
``KORA_SNAPSHOT_INTERVAL_SEC`` env override.

Spec §2(b) says "extend cron/jobs.py OR new kora_cli/snapshot/__
init__.py"; picked the heartbeat-scheduler path (matches what
MCP-CONSUMPTION health-check, alert-notifier, email IMAP poll,
heartbeat probes all do — cheap in-process compute). cron/jobs.py
is the agent-driven cron for external worker processes;
overkill for a pure-Python state projection.

# Web endpoint

``GET /api/snapshot`` returns the snapshot dict verbatim when
fresh on disk; returns ``{"error": "no_snapshot", "stale": true}``
when missing or stale (>10 min). Cockpit + future routing layer
consume this without paying per-source fan-out.

# Read-only contract preserved

This module is a read-only consumer of every source holder. No
mutation of agent/operational_state_holder, agent/cost_state_
holder, kora_cli/heartbeat_probes, or alerts aggregator. The
snapshot is a projection, not a mirror — consumers wanting
authoritative state still read the source-of-truth accessors;
the snapshot is the cheap path for routine status queries.

# Tests

51 new tests pass:
  * 36 state_snapshot (shape + per-section degradation + full-
    degrade resilience + atomic write + read freshness gate +
    is_snapshot_fresh boundary tests + run_snapshot_cycle end-
    to-end + fail-soft on compute/write failure + get_snapshot_
    for_routing convenience)
  * 8 listener (registration in LISTENER_REGISTRY + periodic-task
    registration + cadence env resolution + lifecycle log lines)
  * 4 web endpoint (3-namespace get_kora_home fixture-isolation
    per CC#2 #137; fresh / missing / stale paths + shape pin)

437/437 cross-bucket regression (snapshot + alerts + all
test_listeners). Ruff clean.

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