Standalone Shonar Desktop: vendor portable sources + local engine; decouple from ~/Projects/Shonar

- shared/ = portable Android-origin sources vendored from deferred/desktop-server
  (app/build.gradle.kts srcDir repointed; PlaybackController.kt excluded as Android-only)
- backend/ = bundled-lite engine (SQLite + inline queue); .venv symlinked from the
  old checkout, PYTHONPATH pins THIS backend's code over any editable install
- repoRoot() resolves this project dir (env SHONAR_REPO still wins); desktop-dev.sh
  watches shared/ + backend/
- Verified: :app:compileKotlin + :app:test green (23 tests); engine boots on :8010,
  self-migrates, /healthz ok

backend/shonar/services/ai/_llm.py

@@ -0,0 +1,35 @@
+"""Shared summary contract: one system prompt, one JSON shape.
+
+The model replies with JSON only; partial replies are accepted and missing
+keys default to empty (a terse-but-valid summary beats a failed job).
+Transcript input is truncated to bound context — a way in, not a report.
+"""
+
+from __future__ import annotations
+
+from shonar.services.ai import SummaryResult
+
+SYSTEM_PROMPT = (
+    "You summarize voice recordings for the speaker's own later reference. "
+    "Reply with JSON only, exactly these keys: "
+    '{"short": "1-2 sentences", "detailed": "a faithful paragraph", '
+    '"key_points": [], "decisions": [], "action_items": [], "questions": []}. '
+    "Empty arrays when absent. Never invent names, dates, or commitments "
+    "not stated in the transcript."
+)
+
+MAX_TRANSCRIPT_CHARS = 12_000
+
+
+def build_user_message(transcript: str, title: str | None) -> str:
+    text = transcript[:MAX_TRANSCRIPT_CHARS]
+    if len(transcript) > MAX_TRANSCRIPT_CHARS:
+        text += f"\n\n[truncated from {len(transcript)} chars]"
+    head = f'Title: "{title}"\n\n' if title else ""
+    return head + "Transcript:\n" + text
+
+
+def parse_summary(data: object, model: str) -> SummaryResult:
+    if not isinstance(data, dict):
+        return SummaryResult(model=model)
+    return SummaryResult.from_dict(data, model=model)