Feat v0.3.0 workflow schema redesign + stage CRUD modernization

Drop chat-era columns (persona_id, history_mode) from workflow_stages.
Rename transition_rules → stage_config. Add audience, stage_type,
starlark_hook, branch_rules columns. Update stage_mode CHECK to
(form, review, delegated, automated). All Go stores, handlers,
routing engine, Starlark module, and frontend editors updated.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/database/migrations/postgres/007_workflows.sql

@@ -2,8 +2,9 @@
 -- Switchboard Core — 007 Workflows
 -- ==========================================
 -- Workflow definitions, stages, version snapshots.
--- persona_id kept as nullable TEXT (no FK — personas are extensions now).
--- workflow_assignments dropped (channel-dependent, rebuild as needed).
+-- v0.3.0: persona_id + history_mode dropped (chat vestiges).
+--         transition_rules → stage_config, stage_mode modernized.
+--         Added: audience, stage_type, starlark_hook, branch_rules.
 -- ==========================================
 
 CREATE TABLE IF NOT EXISTS workflows (
@@ -44,15 +45,18 @@ CREATE TABLE IF NOT EXISTS workflow_stages (
     workflow_id        UUID NOT NULL REFERENCES workflows(id) ON DELETE CASCADE,
     ordinal            INTEGER NOT NULL,
     name               TEXT NOT NULL,
-    persona_id         TEXT,
     assignment_team_id UUID REFERENCES teams(id) ON DELETE SET NULL,
     form_template      JSONB NOT NULL DEFAULT '{}',
-    stage_mode         TEXT NOT NULL DEFAULT 'form_only'
-                           CHECK (stage_mode IN ('form_only', 'form_chat', 'review', 'custom')),
-    history_mode       TEXT NOT NULL DEFAULT 'full'
-                           CHECK (history_mode IN ('full', 'summary', 'fresh')),
+    stage_mode         TEXT NOT NULL DEFAULT 'form'
+                           CHECK (stage_mode IN ('form', 'review', 'delegated', 'automated')),
+    audience           TEXT NOT NULL DEFAULT 'team'
+                           CHECK (audience IN ('team', 'public', 'system')),
+    stage_type         TEXT NOT NULL DEFAULT 'simple'
+                           CHECK (stage_type IN ('simple', 'dynamic', 'automated')),
     auto_transition    BOOLEAN NOT NULL DEFAULT false,
-    transition_rules   JSONB NOT NULL DEFAULT '{}',
+    stage_config       JSONB NOT NULL DEFAULT '{}',
+    branch_rules       JSONB NOT NULL DEFAULT '[]',
+    starlark_hook      TEXT,
     surface_pkg_id     TEXT REFERENCES packages(id) ON DELETE SET NULL,
     sla_seconds        INTEGER,
     created_at         TIMESTAMPTZ NOT NULL DEFAULT NOW()