refactor(mode-prompts): migrate search prompt

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

packages/prompts-core/prompts/mode/search.md

@@ -0,0 +1,6 @@
+[search-mode]
+MAXIMIZE SEARCH EFFORT. Launch multiple background agents IN PARALLEL:
+- explore agents (codebase patterns, file structures, ast-grep)
+- librarian agents (remote repos, official docs, GitHub examples)
+Plus direct tools: Grep, ripgrep (rg), ast-grep (sg)
+NEVER stop at first result - be exhaustive.

packages/prompts-core/src/index.ts

@@ -9,3 +9,4 @@ export type {
 export { resolveVariant } from "./variant-resolver"
 export type { ResolveVariantInput } from "./variant-resolver"
 export { loadPrompt, PromptFileNotFoundError, PromptPathTraversalError } from "./loader"
+export { SEARCH_MODE_PROMPT } from "./mode-prompts"

packages/prompts-core/src/mode-prompts.ts

@@ -0,0 +1,7 @@
+import searchModePrompt from "../prompts/mode/search.md" with { type: "text" }
+
+export const SEARCH_MODE_PROMPT = stripFinalLineFeed(searchModePrompt)
+
+function stripFinalLineFeed(prompt: string): string {
+  return prompt.endsWith("\n") ? prompt.slice(0, -1) : prompt
+}