feat(ms-ai-architect): C2.2 valgfritt fritekst-felt free-context.md i onboarding (TDD) [skip-docs]

Spor C / C2.2 (#3, akseptanse K3): fanger et fritt prosa-felt i onboarding og
overflater det (kappet) ambient i hver sesjon.

- lib/user-data.mjs: FREE_CONTEXT_FILE (utenfor ORG_FILES — valgfri, teller ikke
  mot fullføring), collapseProse() surfacer fri kontekst som ÉTT felt uansett
  markdown-struktur (ingen stille drop), capValue() ekstrahert (DRY).
- session-start-context.mjs: leser free-context.md valgfritt (ingen count++).
- onboarding-agent.md: ny Phase 6 (valgfri); onboard.md: prosess/Task/status.
- 11 agenter: uniform 6. bullet (grep 11/11).
- Tester FØR kode: user-data 25/25 (+9), test-hooks 11/11 (+1 K3-ambient).

Gates: validate 239/0/0 · kb-update 200 · kb-eval 100 · kb-integrity 192/192
(220 baseline-warns) · discovery 13/13 · gitleaks 3 pre-eksisterende.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

hooks/scripts/session-start-context.mjs

@@ -14,6 +14,7 @@ import {
 import {
   resolveOrgDir,
   ORG_FILES,
+  FREE_CONTEXT_FILE,
   buildOrgSummary,
 } from '../../scripts/kb-update/lib/user-data.mjs';
 
@@ -130,6 +131,16 @@ function readOrgFiles(dir) {
         }
       }
     }
+    // Optional free-prose context (C2.2): read it for the ambient summary, but
+    // do NOT count it — it is optional and must not affect onboarding completeness.
+    const fp = join(dir, FREE_CONTEXT_FILE);
+    if (existsSync(fp)) {
+      try {
+        files[FREE_CONTEXT_FILE] = readFileSync(fp, 'utf8');
+      } catch {
+        // Unreadable — skip; advisory only
+      }
+    }
   }
   return { files, count };
 }