Sub 18: Orchestrator generic registry wire-up + CadenceEngine pure-trigger-builder correction + collector/pickNextCandidate (Round-2 closer)

Parent Epic

#11831 — Sub 18 of Epic. Round-2 closer per Discussion #11857 Cycle-3.5 B-prime convergence.

Premise

After Subs 15-17 (coordinator extractions) + Sub 19 (MaintenanceBackpressureService), the remaining surface in Orchestrator.mjs is mostly the poll() body + 7 hand-coded scheduling functions (§ I, lines 772-942, ~171 LOC). Sub 18 replaces those with a generic registry + pure collectDueCandidates + pure pickNextCandidate pipeline. Also corrects the CadenceEngine.runIfDue(... executeFn ...) drift per v13-path.md:117 / #11025 pure-trigger-builder spec. Also folds Sub-13's intra-file cleanup (anti-pattern JSDoc strip + collapse remaining singleton refs in § B).

Prescription

1. Registry of coordinator descriptors (metadata only):

{
  taskName        : 'summary' | 'kbSync' | 'backup' | 'primary-dev-sync'
                  | 'dream' | 'goldenPath' | 'swarmHeartbeat' | ...,
  coordinator     : SummarizationCoordinatorService | ... ,
  executionKind   : 'supervised-child-process' | 'service-runner'
                  | 'in-process-async' | 'local-only-service',
  maintenanceClass: 'continuous' | 'heavy' | 'graph-dependent'
                  | 'lightweight-signal' | 'local-only',
  backpressure   : 'none' | 'exclusive-heavy' | 'after-heavy' | ...,
  dependencies   : ['<other-taskName>', ...]
}

2. Boring collector (no policy branching):

collectDueCandidates({registry, context}) → Array<candidate>

Iterates descriptors, calls each getDueTask(context), normalizes triggers, attaches metadata. NO switch(profile) policy body.

3. Pure-function policy gate:

pickNextCandidate({candidates, runningTasks, policyContext}) → candidate | null

Applies (in pipeline): continuous-restart cooldown / exclusive-heavy filtering / golden-path dependency gating / local-only-maintainer eligibility / deployment-profile filtering.

4. CadenceEngine correction: drop executeFn parameter from runIfDue per v13-path.md:117. Trigger-builder only.

5. Orchestrator integration: poll() becomes:

async poll() {
    const candidates = collectDueCandidates({registry: this.registry, context: this.buildContext()});
    const winner    = pickNextCandidate({candidates, runningTasks: this.taskStateService.getRunning(), policyContext: this.buildPolicyContext()});
    if (winner) await this.execute(winner);  // delegates to ProcessSupervisorService OR MaintenanceBackpressureService per executionKind
}

6. Sub-13 cleanup folded in: strip historical-context JSDoc bloat from class @summary; collapse any remaining singleton-alias instance fields (PR #11856 anti-pattern that closed superseded).

Acceptance Criteria

1. Generic registry + collectDueCandidates + pickNextCandidate lands; CadenceEngine corrected to pure trigger-builder per v13-path.md:117
2. Orchestrator.mjs ≤ 400 LOC post-Sub-18 merge (honest, defensible from Discussion #11857 responsibility-map). Aspirational ≤ 300 LOC if Sub 14 #11855 also lands within window
3. Existing 13 mock-heavy Orchestrator.spec.mjs:81-99 tests collapse — coordinators are unit-tested per-sub; Orchestrator integration tests use real coordinators or focused stubs
4. Negative test: collectDueCandidates must NOT cause any state mutation observable in TaskStateService / HealthService / lease state — assertable via spy / before-after snapshot
5. Hard guardrail: collectDueCandidates contains NO switch(profile) policy body — only iteration + normalization + metadata attachment
6. Sub-13 cleanup folded in: class @summary stripped of "Service-DI 4-way classification" historical narrative + "No configure(). No DEFAULT_X_*_MS..." negative trailer + any remaining Class A/B/C/D section divider comments
7. poll() calls MaintenanceBackpressureService.acquireLeaseAndExecute({...}) and .executeWithGoldenPathDependencyGate({...}) (Sub 19 lands first; Sub 18 wires)

Compound revalidationTrigger (per Discussion #11857 AC 11)

• If Orchestrator.mjs LOC drifts above 500 within 60 days of Sub-18 merge → file revalidation ticket to assess Round-3 decomposition
• If Sub 19 cannot extract 70% of §E-H without broader split → resolved by Sub 19's own AC 6 BEFORE Sub-18 lands

Avoided Traps

• NO singleton-alias bag in the registry
• NO collector owning writes
• NO switch(profile) in collector
• NO bootstrap split bundled (deferred to Round-3)
• NO M4 broader feature work

Depends on

Subs 15, 16, 17 (coordinator extractions) + Sub 19 (MaintenanceBackpressureService).

Unblocks

Round-2 closure. Round-3 candidates evaluated post-measurement: bootstrap split / InProcessTaskRunner extraction if metrics show them as the dominant remaining surface.

Authority

Discussion #11857 Cycle-3.5 GPT [GRADUATION_APPROVED] + operator ratify.

Authored by: [Claude Opus 4.7] (Claude Code)