feat(coder): orchestrator advanced flow patterns

- TriggerRule type (all_success/one_success/all_done) for parallel deps
- Variable substitution ($stepId.output.field) in agent step prompts
- Approval gate step kind (pauses flow via permission frames)
- flow_step_events table for append-only event-sourced step log
- evaluateTriggerRule pure function in flow-runner-decisions

apps/coder/src/services/flow-runner-decisions.ts

@@ -22,7 +22,7 @@
  * "Settled" = done ∪ skipped ∪ excluded. Only settled deps unblock a step;
  * an inFlight dep does NOT (the runner waits for its terminal callback).
  */
-import type { Flow, Step, StepContext } from '../conductor/types.js';
+import type { Flow, Step, StepContext, TriggerRule } from '../conductor/types.js';
 
 export interface SchedulerState {
   /** step ids that completed successfully (results available) */
@@ -62,7 +62,7 @@ export function readySteps(flow: Flow, state: SchedulerState): Step[] {
       !state.skipped.has(s.id) &&
       !state.inFlight.has(s.id) &&
       !state.excluded.has(s.id) &&
-      (s.deps ?? []).every((d) => isSatisfied(state, d)),
+      ((s.deps ?? []).length === 0 || evaluateTriggerRule(s.deps ?? [], state.done, state.skipped, state.excluded, s.trigger_rule)),
   );
 }
 
@@ -167,6 +167,32 @@ export function shouldFailOnMissingAgent(agent: string, modeId: string | null):
   return agent === 'qwen' && modeId === 'plan';
 }
 
+/**
+ * Evaluate a trigger rule against dependency results.
+ * - all_success: every dep must be done (not skipped/failed)
+ * - one_success: at least one dep must be done
+ * - all_done: every dep must be settled regardless of outcome
+ */
+export function evaluateTriggerRule(
+  deps: string[],
+  done: ReadonlySet<string>,
+  skipped: ReadonlySet<string>,
+  excluded: ReadonlySet<string>,
+  rule?: TriggerRule,
+): boolean {
+  if (deps.length === 0) return true;
+  const satisfied = new Set([...done, ...skipped, ...excluded]);
+
+  switch (rule ?? 'all_success') {
+    case 'all_success':
+      return deps.every((d) => done.has(d) || skipped.has(d) || excluded.has(d));
+    case 'one_success':
+      return deps.some((d) => done.has(d));
+    case 'all_done':
+      return deps.every((d) => satisfied.has(d));
+  }
+}
+
 /**
  * Reconcile every step of an in-flight run for startup resume. Returns one
  * decision per step. Pure — no IO.