fix(#1913): derive workstream progress status from shipped signals (#1916)

workstream progress trusted the mutable STATE.md `Status` field, so a
shipped/archived milestone whose field was left at `executing` was reported
as executing — a stale hand-maintained field became the source of truth
instead of the authoritative archive/tag/ROADMAP signals.

Derive status in the inventory builder from a milestoneShipped signal
(archived milestone snapshot under milestones/, or a SHIPPED marker in the
workstream ROADMAP), collected by inspectWorkstream. The inventory now
reports `status_source` (field|derived) and `status_conflict` (true when
the derived value disagrees with the stale field), and a shipped workstream
is never reported executing.

- src/workstream-inventory-builder.cts: milestoneShipped input + status_source/status_conflict outputs + derivation
- src/workstream-inventory.cts: workstreamMilestoneShipped() signal detector wired into inspectWorkstream
- tests/workstream-inventory.test.cjs: regression (builder unit + inspectWorkstream integration + negative)

Closes #1913

tests/workstream-inventory.test.cjs

@@ -0,0 +1,103 @@
+'use strict';
+
+// Regression + projection coverage for the workstream-inventory module.
+// #1913: status must be derived from authoritative shipped signals (milestone
+// archive snapshot / ROADMAP SHIPPED marker), not trusted from the mutable
+// STATE.md `Status` field.
+
+const { describe, test, before, after } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('fs');
+const path = require('path');
+const { cleanup } = require('./helpers.cjs');
+const { createFixture, seedWorkstream } = require('./fixtures/index.cjs');
+const { buildWorkstreamInventory } = require('../gsd-core/bin/lib/workstream-inventory-builder.cjs');
+const { inspectWorkstream } = require('../gsd-core/bin/lib/workstream-inventory.cjs');
+
+const STALE_STATE = 'status: executing\n';
+const IN_PROGRESS_ROADMAP =
+  '# Roadmap\n## Milestones\n- v2.0 Test — IN PROGRESS\n## Phases\n### Phase 1: Foo\n**Goal:** foo\n';
+
+describe('#1913 — workstream status derived from authoritative shipped signals', () => {
+  let tmpDir;
+  before(() => { tmpDir = createFixture(); });
+  after(() => cleanup(tmpDir));
+
+  test('builder: milestoneShipped overrides a stale executing field (derived + conflict)', () => {
+    const inv = buildWorkstreamInventory({
+      name: 'ws-a',
+      projectDir: tmpDir,
+      workstreamDir: path.join(tmpDir, '.planning', 'workstreams', 'ws-a'),
+      phaseDirNames: [],
+      activeWorkstreamName: '',
+      phaseFilesCounts: [],
+      roadmapPhaseCount: 0,
+      stateProjection: { status: 'executing', current_phase: null, last_activity: null },
+      filesExist: { roadmap: true, state: true, requirements: true },
+      milestoneShipped: true,
+    });
+    assert.equal(inv.status, 'milestone complete');
+    assert.equal(inv.status_source, 'derived');
+    assert.equal(inv.status_conflict, true);
+  });
+
+  test('builder: no shipped signal → field status, no conflict', () => {
+    const inv = buildWorkstreamInventory({
+      name: 'ws-b',
+      projectDir: tmpDir,
+      workstreamDir: path.join(tmpDir, '.planning', 'workstreams', 'ws-b'),
+      phaseDirNames: [],
+      activeWorkstreamName: '',
+      phaseFilesCounts: [],
+      roadmapPhaseCount: 0,
+      stateProjection: { status: 'executing', current_phase: null, last_activity: null },
+      filesExist: { roadmap: true, state: true, requirements: true },
+      milestoneShipped: false,
+    });
+    assert.equal(inv.status, 'executing');
+    assert.equal(inv.status_source, 'field');
+    assert.equal(inv.status_conflict, false);
+  });
+
+  test('inspectWorkstream: shipped archive snapshot + stale executing STATE → derived complete', () => {
+    const wsDir = seedWorkstream(tmpDir, { name: 'ws-archived' });
+    fs.writeFileSync(path.join(wsDir, 'STATE.md'), STALE_STATE);
+    fs.writeFileSync(path.join(wsDir, 'ROADMAP.md'), IN_PROGRESS_ROADMAP);
+    // Authoritative shipped signal: an archived milestone snapshot.
+    fs.mkdirSync(path.join(wsDir, 'milestones'), { recursive: true });
+    fs.writeFileSync(path.join(wsDir, 'milestones', 'v1.0-ROADMAP.md'), '# v1.0 archived\n');
+
+    const inv = inspectWorkstream(tmpDir, 'ws-archived', { active: null });
+    assert.ok(inv, 'inventory should be produced');
+    assert.equal(inv.status, 'milestone complete');
+    assert.equal(inv.status_source, 'derived');
+    assert.equal(inv.status_conflict, true);
+  });
+
+  test('inspectWorkstream: ROADMAP SHIPPED marker + stale executing STATE → derived complete', () => {
+    const wsDir = seedWorkstream(tmpDir, { name: 'ws-shipped' });
+    fs.writeFileSync(path.join(wsDir, 'STATE.md'), STALE_STATE);
+    fs.writeFileSync(
+      path.join(wsDir, 'ROADMAP.md'),
+      '# Roadmap\n## Milestones\n<details><summary>✅ v1.0 MVP - SHIPPED 2026-06-01</summary>\n## Phases\n### Phase 1: Foo\n**Goal:** foo\n'
+    );
+
+    const inv = inspectWorkstream(tmpDir, 'ws-shipped', { active: null });
+    assert.ok(inv, 'inventory should be produced');
+    assert.equal(inv.status, 'milestone complete');
+    assert.equal(inv.status_source, 'derived');
+    assert.equal(inv.status_conflict, true);
+  });
+
+  test('inspectWorkstream: no shipped signals + executing STATE → field status, no conflict', () => {
+    const wsDir = seedWorkstream(tmpDir, { name: 'ws-active' });
+    fs.writeFileSync(path.join(wsDir, 'STATE.md'), STALE_STATE);
+    fs.writeFileSync(path.join(wsDir, 'ROADMAP.md'), IN_PROGRESS_ROADMAP);
+
+    const inv = inspectWorkstream(tmpDir, 'ws-active', { active: null });
+    assert.ok(inv, 'inventory should be produced');
+    assert.equal(inv.status, 'executing');
+    assert.equal(inv.status_source, 'field');
+    assert.equal(inv.status_conflict, false);
+  });
+});