feat(task): added read-summarize override for subagents

- Parsed `read-summarize` frontmatter into `readSummarize` field.
- Applied `read.summarize.enabled: false` override on isolated subagent settings.
- Disabled summarization for `explore` and `librarian` agents.

packages/coding-agent/src/prompts/agents/librarian.md

@@ -4,6 +4,7 @@ description: Researches external libraries and APIs by reading source code. Retu
 tools: read, search, find, bash, lsp, web_search, ast_grep
 model: pi/smol
 thinking-level: minimal
+read-summarize: false
 output:
   properties:
     answer: