release: 2.0.0 — the agent harness operating system

Graduate 2.0.0-rc.1 to stable. Bump version across package, plugin,
marketplace, OpenCode, agent metadata, VERSION, and all localized docs.
Add 2.0.0 release notes + README sections (en/zh/pt-BR/tr), CHANGELOG
entry, and the ECC community Discord bot (dependency-free gateway client
+ guild command registrar). Update copilot-support and release-surface
tests for the sponsored-review migration and the 2.0.0 surface.

.opencode/plugins/ecc-hooks.ts

@@ -453,7 +453,7 @@ export const ECCHooksPlugin: ECCHooksPluginFn = async ({
       const contextBlock = [
         "# ECC Context (preserve across compaction)",
         "",
-        "## Active Plugin: ECC v2.0.0-rc.1",
+        "## Active Plugin: ECC v2.0.0",
         "- Hooks: file.edited, tool.execute.before/after, session.created/idle/deleted, shell.env, compacting, permission.ask",
         "- Tools: run-tests, check-coverage, security-audit, format-code, lint-check, git-summary, changed-files",
         "- Agents: 13 specialized (planner, architect, tdd-guide, code-reviewer, security-reviewer, build-error-resolver, e2e-runner, refactor-cleaner, doc-updater, go-reviewer, go-build-resolver, database-reviewer, python-reviewer)",