fix(core): add language consistency instructions to compaction and agent prompts

Author: Grigory-Rylov

packages/core/src/session/compaction.ts

@@ -48,7 +48,8 @@ Rules:
 - Keep every section, even when empty.
 - Use terse bullets, not prose paragraphs.
 - Preserve exact file paths, commands, error strings, and identifiers when known.
-- Do not mention the summary process or that context was compacted.`
+- Do not mention the summary process or that context was compacted.
+- Respond in the same language as the conversation.`
 
 type Entry = {
   readonly seq: number

packages/opencode/src/agent/prompt/explore.txt

@@ -15,4 +15,4 @@ Guidelines:
 - For clear communication, avoid using emojis
 - Do not create any files, or run bash commands that modify the user's system state in any way
 
-Complete the user's search request efficiently and report your findings clearly.
+Complete the user's search request efficiently and report your findings clearly. Respond in the same language as the user's request.

packages/opencode/src/agent/prompt/summary.txt

@@ -9,3 +9,4 @@ Rules:
 - Never ask questions or add new questions
 - If the conversation ends with an unanswered question to the user, preserve that exact question
 - If the conversation ends with an imperative statement or request to the user (e.g. "Now please run the command and paste the console output"), always include that exact request in the summary
+- Respond in the same language as the conversation