…g sources

Flips ``GET /api/alerts/current`` from the v1 stub (PR #134) to a
real aggregator that pulls from 5 sources:

  * OperationalStateHolder (PAUSED / STOPPED)
  * Cost-ladder holder (WARN_75 / DOWNSHIFT_90 / HARD_STOP_100)
  * Audit JSONL (webhook.dead_letter / mcp.tool_called
    result=capability_denied / reasoning.tool_called
    tool_status=execution_error / slack_dm.reply_failed) — uses
    kora_cli.audit.jsonl_reader.read_audit_entries from #141
  * HealthRollupHolder (not directly emitted today; per-service
    snapshot data drives service_unhealthy below)
  * Heartbeat probe snapshots (Vercel / Sentry / Doppler /
    Supabase / Fly via current_service_snapshots() from #118)

10 rules emit operator-facing alerts:

  cost_ladder_warned       warning
  cost_ladder_downshifted  warning
  cost_ladder_halted       critical
  operator_paused          critical
  operator_stopped         critical
  webhook_dead_letters_24h warning  (threshold > 5)
  capability_denied_24h    info     (threshold > 10, forward-compat)
  reasoning_errors_24h     warning  (threshold > 5)
  slack_dm_reply_failed_24h warning (threshold > 3)
  service_unhealthy        warning/critical (per affected service)

Fail-soft per-source: each rule helper is wrapped in try/except;
a single source failure (holder uninitialized, JSONL unreadable,
probe accessor crash) NEVER bubbles a 500 to the operator. Outer
``compute_active_alerts`` also catches helper-bypass exceptions
as defense in depth.

Sort: severity rank (critical → warning → info) then by alert id
for stable intra-tier ordering.

K-DG drift caught + documented inline (vs bucket spec §1):
  * ``get_operational_state_holder()`` (spec) → actual symbol is
    ``get_holder()`` in agent.operational_state_holder
  * ``get_health_holder()`` (spec) → actual is
    ``get_health_rollup_holder()`` in agent.health_rollup_holder
  * ``current_pct_used()`` / ``active_rung()`` are METHODS on
    CostStateHolder (#126 PM-locked catch)
  * ``holder.current`` is @Property on OperationalStateHolder;
    ``.primary_state`` is bare enum field on the inner dataclass
    (#112 catch)
  * HealthRollup is a frozen dataclass with bare field names
    ``overall`` / ``control_plane`` / ``worker`` — not @Property
    (#112 catch)
  * Audit reader at ``kora_cli/audit/jsonl_reader.py:58`` accepts
    ``seam=`` + ``since=`` kwargs (per #141)

Forward-compat note: ``capability_denied_24h`` rule's matcher
keys on ``details.result == "capability_denied"``. Today the
audit emit at ``mcp_tools.py:714`` runs AFTER the cap-gate at
``mcp.py:181``, so denial responses are NOT logged — rule emits
0 alerts in the current state (documented in aggregator + test).
When a follow-on bucket adds audit-on-denial the rule activates
automatically.

CC#2 #137 fixture-isolation discipline applied (3-namespace
``get_kora_home`` monkeypatch + reset all 5 aggregator sources
to baseline in the existing PR #134 stub-test fixture).

3-layer SECURITY contract preserved from PR #134: title/detail
plain text, no PII/token shapes in walk-payload sweep, TS
interface enforcement.

28 new aggregator tests (per-rule trigger + severity + fail-soft
+ sort + endpoint integration + walk-payload) + 15 preserved
shape/security tests in test_web_server_alerts.py. 123/123
cross-bucket regression (alerts + email panel + slack-dm panel).
Ruff clean.

After this lands every operator-facing panel reads real data.
Last major stub-flip in the cockpit.

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