docs: add openspec proposals for memory v2 and orchestrator flow patterns

openspec/changes/orchestrator-flow-advanced/design.md

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+# Orchestrator Advanced Flows — Design
+
+## Architecture
+
+```
+┌───────────── Step dispatch ─────────────────┐
+│                                              │
+│  Flow-runner resolves step:                  │
+│    1. Check trigger_rule on deps             │
+│    2. Substitute $vars in prompt             │
+│    3. If approval gate → pause for user      │
+│    4. INSERT task row → dispatcher picks up  │
+│    5. On terminal: append to event log       │
+│    6. Advance next ready step                │
+│                                              │
+└──────────────────────────────────────────────┘
+```
+
+## Type Changes
+
+### `apps/coder/src/conductor/types.ts`
+
+```typescript
+export type TriggerRule = 'all_success' | 'one_success' | 'all_done';
+
+export interface Step {
+  id: string;
+  kind: StepKind | 'approval';         // + new kind
+  deps?: string[];
+  trigger_rule?: TriggerRule;            // NEW: default 'all_success'
+  agent?: string;
+  run: (ctx: StepContext) => string | Promise<string>;
+  when?: (ctx: StepContext) => boolean;
+}
+```
+
+### `apps/coder/src/services/flow-runner.ts`
+
+| Change | Detail |
+|--------|--------|
+| Trigger evaluation | Before dispatching a step, check deps statuses against `trigger_rule`. Skip if conditions not met |
+| Variable substitution | Scan prompt for `$word.word` patterns, resolve from previous step outputs |
+| Approval gate | When `step.kind === 'approval'`, insert a `tasks` row with `state='blocked'` and publish a `permission_requested` WS frame. Wait for `permission_resolved` to unblock |
+| Event log | Append-only per-step events: `{ step_id, event: 'started'|'completed'|'failed'|'paused'|'resumed', at: timestamp }` in `flow_step_events` table |
+
+## Schema
+
+```sql
+CREATE TABLE IF NOT EXISTS flow_step_events (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  run_id UUID NOT NULL REFERENCES flow_runs(id),
+  step_id VARCHAR(64) NOT NULL,
+  event VARCHAR(32) NOT NULL,  -- started, completed, failed, paused, resumed, skipped
+  payload JSONB,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT clock_timestamp()
+);
+```
+
+## Resolution Order
+
+1. Collect all completed steps in the run
+2. For each unstarted step whose deps are met:
+   - Evaluate `trigger_rule` against dep statuses
+   - If met → advance the step (with variable substitution)
+   - If not met → skip (for `one_success`, mark it complete when any dep succeeds)
+3. For approval gates: pause, publish frame, wait for user response
+
+## Rollback
+
+All changes are additive to the Step type. Existing flows without `trigger_rule` default to `all_success`, preserving current behavior. Approval gates are opt-in per step definition.