P0 fix: content/ not in image crashed API boot; harden garnish + preflight

ROOT CAUSE: the Dockerfile copied src/poller/scripts/supabase but NOT
content/. mediaEngine.js read content/stark-lines.json with an unguarded
module-load readFileSync; ENOENT in the image threw at require time, and
via app.js → routes/desk → deskService → mediaEngine that crashed the
ENTIRE API at boot. The Coolify healthcheck rolled back to the last
healthy image (4d2b27d), so every deploy since 219167e silently served a
14-hour-old build — S11 live tracking, S6 API code, the settlement boot
line, and SNAPSHOT_EXPECTED_INTERVAL were all merged but NOT running.

FIX (one train):
1. Dockerfile COPYs content/ into the runner image.
2. mediaEngine: stark-lines.json is OPTIONAL (garnish, never load-bearing)
   — loadStark() try/catch → {} → posts render without the Stark kicker,
   never a crash. Belt AND suspenders with #1.
3. src/preflight.js (§A4): boot prints '[preflight] OK' or 'DEGRADED'
   naming exactly what content/env is missing — before the healthcheck
   can fail silently. Run first in server.js.
4. Full fragility sweep: mediaEngine was the ONLY unguarded module-load
   file read; coachSignals (config/coaches.json) was already lazy +
   try/catch + copied. No others.

Verified: requiring app.js + deskService + mediaEngine with
stark-lines.json ABSENT now boots clean (reproduced the exact prod
failure). 2757 -> 2763 tests (tests/unit/bootResilience.test.js).

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

src/services/mediaEngine.js

@@ -20,7 +20,24 @@
 const fs = require('fs');
 const path = require('path');
 
-const STARK = JSON.parse(fs.readFileSync(path.join(__dirname, '..', '..', 'content', 'stark-lines.json'), 'utf8'));
+// Session 65 (P0 deploy fix) — the Stark-layer library is a GARNISH, never
+// load-bearing. This used to be an unguarded module-load readFileSync; when
+// the file wasn't in the container image it threw at require time, which
+// (via app.js → routes/desk → deskService → here) crashed the WHOLE API at
+// boot and silently rolled the deploy back for 14 hours. A witty kicker is
+// not allowed to take down the record. Missing/corrupt file → empty library
+// → every format posts WITHOUT the Stark line (starkLine returns null),
+// which is a valid, still-VOICE-compliant post. Never throws.
+const STARK_PATH = path.join(__dirname, '..', '..', 'content', 'stark-lines.json');
+function loadStark() {
+  try {
+    return JSON.parse(fs.readFileSync(STARK_PATH, 'utf8'));
+  } catch (e) {
+    console.warn(`[mediaEngine] stark-lines.json unavailable (${e.code || e.message}); posting without the Stark layer.`);
+    return {};
+  }
+}
+const STARK = loadStark();
 
 // ---- VOICE lint -----------------------------------------------------------
 const BANNED_PATTERNS = [