feat(system-prompt): wire into turn flow + compaction + API routes

session-orchestrator:
- Wire systemPromptService as optional dep (lazy via host.getService)
- Regular turn: construct on first turn (new conversation), get on subsequent
  turns, set on providerOpts.systemPrompt (cache-safe)
- Compaction: construct (fresh resolve) + append COMPACTION_SYSTEM_PROMPT
- 12 new tests (construct/get/service-unavailable/compaction)

transport-http:
- GET /system-prompt (returns template or DEFAULT_TEMPLATE)
- PUT /system-prompt (validate + setTemplate, 503 when unavailable)
- GET /system-prompt/variables (static catalog, always available)
- 6 new tests

system-prompt service: added getTemplate/setTemplate to interface + impl.

1396 vitest pass. typecheck + biome clean.

1 files changed, 2 insertions, 1 deletions

diff --git a/packages/session-orchestrator/tsconfig.json b/packages/session-orchestrator/tsconfig.json
index 782c1c8..2ca3bd2 100644
--- a/packages/session-orchestrator/tsconfig.json
+++ b/packages/session-orchestrator/tsconfig.json
@@ -6,6 +6,7 @@
 		{ "path": "../kernel" },
 		{ "path": "../conversation-store" },
 		{ "path": "../credential-store" },
-		{ "path": "../message-queue" }
+		{ "path": "../message-queue" },
+		{ "path": "../system-prompt" }
 	]
 }