feat(ce-update): add plugin version check skill and ce_platforms filtering (#532)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plugins/compound-engineering/AGENTS.md

@@ -136,7 +136,7 @@ Why: shell-heavy exploration causes avoidable permission prompts in sub-agent wo
 
 - [ ] Never instruct agents to use `find`, `ls`, `cat`, `head`, `tail`, `grep`, `rg`, `wc`, or `tree` through a shell for routine file discovery, content search, or file reading
 - [ ] Describe tools by capability class with platform hints — e.g., "Use the native file-search/glob tool (e.g., Glob in Claude Code)" — not by Claude Code-specific tool names alone
-- [ ] When shell is the only option (e.g., `ast-grep`, `bundle show`, git commands), instruct one simple command at a time — no chaining (`&&`, `||`, `;`) and no error suppression (`2>/dev/null`, `|| true`). Simple pipes (e.g., `| jq .field`) and output redirection (e.g., `> file`) are acceptable when they don't obscure failures
+- [ ] When shell is the only option (e.g., `ast-grep`, `bundle show`, git commands), instruct one simple command at a time — no chaining (`&&`, `||`, `;`) and no error suppression (`2>/dev/null`, `|| true`). Simple pipes (e.g., `| jq .field`) and output redirection (e.g., `> file`) are acceptable when they don't obscure failures. **Exception:** `!` backtick pre-resolution commands may use error suppression and `||` fallbacks to produce clean sentinel values (e.g., `|| echo '__FAILED__'`), since these run at load time and the model needs a parseable signal, not raw stderr
 - [ ] Do not encode shell recipes for routine exploration when native tools can do the job; encode intent and preferred tool classes instead
 - [ ] For shell-only workflows (e.g., `gh`, `git`, `bundle show`, project CLIs), explicit command examples are acceptable when they are simple, task-scoped, and not chained together