Bootstrap StagePilot baseline for slot domain migration

Initialize baseline seed, four baseline docs (project-structure,
runtime-flows, interface-contract, data-model), and the active
discovery/srs/batches/releases indexes. Content derived from the
trex-orbit slot pure-domain migration plan (trex-core as a new base,
pure domain only).

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

docs/discovery/index.md

@@ -0,0 +1,8 @@
+# Discovery 전체 인덱스
+
+<!-- 아래 테이블은 /new-discovery 실행 시 자동 갱신된다. 수동 편집 금지. -->
+
+## Discovery 목록
+
+| ID | 날짜 | 이슈명 | 문서 | 상태 |
+|---|---|---|---|---|