step 4: fresh kernel-only migrations

Deleted all 23+23 old chat-switchboard migration files.
Wrote 9+9 clean kernel-only migrations in postgres/ and sqlite/ subdirs.

27 tables per dialect covering all 20 store interfaces:
  001: users, refresh_tokens, policies, settings, presence, oidc
  002: teams, team_members, groups, group_members
  003: packages, package_user_settings, ext_permissions, ext_data_tables
  004: ext_connections, ext_dependencies, resource_grants
  005: notifications, notification_preferences
  006: audit_log
  007: workflows, workflow_stages, workflow_versions
  008: tasks, task_runs
  009: ws_tickets, rate_limit_counters

Dropped: providers, personas, channels, messages, knowledge, notes,
memory, workspaces, projects, folders, files, usage_log, tool_health,
workflow_assignments, ext_view_channels.

Schema changes vs old:
  - pgvector extension removed (no KB embeddings)
  - resource_grants: resource_type CHECK removed (open-ended)
  - workflow_stages: persona_id kept as nullable TEXT (no FK)
  - workflow_stages: stage_mode default=form_only, added custom
  - tasks: dropped output_channel_id, provider_config_id columns
  - tasks: task_type removed prompt, output_mode: notification|webhook|log
  - task_runs: dropped channel_id
  - platform_policies: kernel-only seeds
  - global_settings: kernel-only seeds, site name=Switchboard Core
  - Everyone group: kernel permissions (extension.use, workflow.submit)

-2815/+487 lines.

server/database/migrations/postgres/008_tasks.sql

@@ -0,0 +1,69 @@
+-- ==========================================
+-- Switchboard Core — 008 Tasks
+-- ==========================================
+-- Task scheduling and run history.
+-- Stripped: persona_id (kept nullable, no FK), output_channel_id,
+-- provider_config_id. Output modes: notification | webhook | log.
+-- ==========================================
+
+CREATE TABLE IF NOT EXISTS tasks (
+    id                 UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    owner_id           UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    team_id            UUID REFERENCES teams(id) ON DELETE SET NULL,
+    name               TEXT NOT NULL,
+    description        TEXT DEFAULT '',
+    scope              TEXT NOT NULL DEFAULT 'personal'
+                       CHECK (scope IN ('personal', 'team', 'global')),
+    task_type          TEXT NOT NULL DEFAULT 'action'
+                       CHECK (task_type IN ('action', 'workflow', 'system')),
+    system_function    TEXT DEFAULT '',
+    persona_id         TEXT,
+    model_id           TEXT,
+    system_prompt      TEXT DEFAULT '',
+    user_prompt        TEXT DEFAULT '',
+    workflow_id        UUID REFERENCES workflows(id) ON DELETE SET NULL,
+    tool_grants        JSONB,
+    schedule           TEXT NOT NULL,
+    timezone           TEXT NOT NULL DEFAULT 'UTC',
+    is_active          BOOLEAN NOT NULL DEFAULT true,
+    trigger_token      TEXT UNIQUE,
+    max_tokens         INTEGER NOT NULL DEFAULT 4096,
+    max_tool_calls     INTEGER NOT NULL DEFAULT 10,
+    max_wall_clock     INTEGER NOT NULL DEFAULT 300,
+    output_mode        TEXT NOT NULL DEFAULT 'log'
+                       CHECK (output_mode IN ('notification', 'webhook', 'log')),
+    webhook_url        TEXT,
+    webhook_secret     TEXT,
+    notify_on_complete BOOLEAN NOT NULL DEFAULT false,
+    notify_on_failure  BOOLEAN NOT NULL DEFAULT true,
+    last_run_at        TIMESTAMPTZ,
+    next_run_at        TIMESTAMPTZ,
+    run_count          INTEGER NOT NULL DEFAULT 0,
+    created_at         TIMESTAMPTZ NOT NULL DEFAULT now(),
+    updated_at         TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_tasks_next_run ON tasks(next_run_at) WHERE is_active = true;
+CREATE INDEX IF NOT EXISTS idx_tasks_owner ON tasks(owner_id);
+CREATE INDEX IF NOT EXISTS idx_tasks_team ON tasks(team_id);
+CREATE UNIQUE INDEX IF NOT EXISTS idx_tasks_trigger_token
+    ON tasks(trigger_token) WHERE trigger_token IS NOT NULL;
+
+-- ── Task Runs ───────────────────────────────
+
+CREATE TABLE IF NOT EXISTS task_runs (
+    id               UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    task_id          UUID NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
+    status           TEXT NOT NULL DEFAULT 'running'
+                     CHECK (status IN ('queued', 'running', 'completed', 'failed', 'budget_exceeded', 'cancelled')),
+    trigger_payload  TEXT,
+    started_at       TIMESTAMPTZ NOT NULL DEFAULT now(),
+    completed_at     TIMESTAMPTZ,
+    tokens_used      INTEGER DEFAULT 0,
+    tool_calls       INTEGER DEFAULT 0,
+    wall_clock       INTEGER DEFAULT 0,
+    error            TEXT
+);
+
+CREATE INDEX IF NOT EXISTS idx_task_runs_task ON task_runs(task_id);
+CREATE INDEX IF NOT EXISTS idx_task_runs_status ON task_runs(task_id, status);