chore: prepare v1.9.0 release (#666)

- Bump version to 1.9.0 in package.json, package-lock.json, .opencode/package.json
- Add v1.9.0 changelog with 212 commits covering selective install architecture,
  6 new agents, 15+ new skills, session/state infrastructure, observer fixes,
  12 language ecosystems, and community contributions
- Update README with v1.9.0 release notes and complete agents tree (27 agents)
- Add pytorch-build-resolver to AGENTS.md agent table
- Update documentation counts to 27 agents, 109 skills, 57 commands
- Update version references in zh-CN README
- All 1421 tests passing, catalog counts verified

AGENTS.md

@@ -2,6 +2,8 @@
 
 This is a **production-ready AI coding plugin** providing 27 specialized agents, 109 skills, 57 commands, and automated hook workflows for software development.
 
+**Version:** 1.9.0
+
 ## Core Principles
 
 1. **Agent-First** — Delegate to specialized agents for domain tasks
@@ -39,6 +41,7 @@ This is a **production-ready AI coding plugin** providing 27 specialized agents,
 | harness-optimizer | Harness config tuning | Reliability, cost, throughput |
 | rust-reviewer | Rust code review | Rust projects |
 | rust-build-resolver | Rust build errors | Rust build failures |
+| pytorch-build-resolver | PyTorch runtime/CUDA/training errors | PyTorch build/training failures |
 | typescript-reviewer | TypeScript/JavaScript code review | TypeScript/JavaScript projects |
 
 ## Agent Orchestration
@@ -139,7 +142,7 @@ Troubleshoot failures: check test isolation → verify mocks → fix implementat
 
 ```
 agents/          — 27 specialized subagents
-skills/          — 108 workflow skills and domain knowledge
+skills/          — 109 workflow skills and domain knowledge
 commands/        — 57 slash commands
 hooks/           — Trigger-based automations
 rules/           — Always-follow guidelines (common + per-language)