refactor(model-pool): scope disabled-models by company; cascade on delete (v42)

The per-connector "enabled/disabled model" settings lived under a
global key in the settings key-value table
(`disabled_models:${connectorId}`). No company dimension. Deleting a
company left the pool choices behind, and creating a new company
silently inherited them — the visible symptom was "onboarding's team-
model configuration survives company deletion and pollutes the next
company's CEO model list."

Root fix, not a cleanup hook: the storage becomes a real relational
table with `(company_id, connector_id)` primary key and an
`ON DELETE CASCADE` FK from `companies`. Company deletion wipes pool
config by construction; no cleanup step in `deleteCompany()` can
drift.

Schema (migration v42):
- CREATE TABLE connector_model_pool_settings (company_id, connector_id,
  disabled_models_json, updated_at), PK (company_id, connector_id),
  FK companies(id) ON DELETE CASCADE.
- Drop every `settings.disabled_models:*` key — these were the bug's
  residue; there is no right company to attribute them to, so the
  migration clears them. Users re-select on next onboarding.

API surgery — every reader/writer now takes companyId:
- db.getDisabledModels(companyId, connectorId)
- db.setDisabledModels(companyId, connectorId, models)
- db.hasModelPoolSettings(companyId, connectorId)
- connector-model-policy: getConnectorModelPolicy(deps, companyId,
  connectorId); validateConnectorModelSelection(deps, companyId,
  connectorId, model)
- model-dispatch: listEnabledModels(companyId, deps);
  pickModelForAgent resolves companyId from agent.companyId
- orchestration heartbeat/task-runner/turn-context/run-dispatch pass
  the agent's or run's companyId through to the policy deps
- IPC schema: connectorDisabledModelsSchema gains companyId; new
  connectorModelPoolQuerySchema pairs companyId+connectorId for reads

Onboarding becomes commit-on-launch:
- useConnectorModelSelection no longer persists via IPC during
  onboarding. Toggles mutate local state; it exposes `poolSelections`
  to the wizard.
- bootstrapOnboardingSchema gains connectorPoolSelections. The
  onboarding service saves the company first, then persists each
  per-connector disabled list scoped to the new company id — CEO
  model validation runs against the company's freshly-persisted pool,
  not some stale global.
- IPC setConnectorDisabledModels now requires companyId; the only
  consumer was onboarding, which no longer calls it at all.
- Main-side listConnectorModels returns the raw provider catalog
  (no pool filtering), since that IPC is used from onboarding where
  no company exists yet; pool filtering happens at dispatch time.

saveConnector IPC drops the per-company pool validation — connector
config is a global hint, company-scoped enforcement belongs at run
dispatch where the company is known.

Tests: 603/603 green. Typecheck clean. Integration tests rewritten
to set the pool via connectorPoolSelections on bootstrap input, not
a pre-bootstrap global setDisabledModels call.

src/main/database/schema.ts

@@ -6,6 +6,7 @@ import { createMigrationsV35V37 } from "./migrations/v35-v37";
 import { createMigrationsV38V39 } from "./migrations/v38-v39";
 import { createMigrationsV40V40 } from "./migrations/v40-v40";
 import { createMigrationsV41V41 } from "./migrations/v41-v41";
+import { createMigrationsV42V42 } from "./migrations/v42-v42";
 import {
   columnExists,
   nowIso,
@@ -178,6 +179,7 @@ export function runMigrations(
     ...createMigrationsV38V39(deps),
     ...createMigrationsV40V40(deps),
     ...createMigrationsV41V41(deps),
+    ...createMigrationsV42V42(deps),
   ];
 
   for (const migration of migrations) {