fix(opencode): add resolvable package entry and loadable in-place sources

Root package.json declared no main or exports, so OpenCode npm plugin
resolution (import.meta.resolve) failed and the plugin was silently
skipped (#3127). The .opencode TypeScript sources imported siblings
with .js specifiers that only exist after compilation, so the home
install, which loads the .ts files in place, crashed the tool registry
with ERR_MODULE_NOT_FOUND (#3112).

Declare main/types/exports on the root package pointing at the
compiled plugin entry, switch the sources to .ts specifiers, and
enable allowImportingTsExtensions with rewriteRelativeImportExtensions
so the emitted dist keeps working .js specifiers. Add smoke tests that
build the package, resolve and import the entry by name from a temp
install, and verify every in-place relative import resolves.

Fixes #3127
Fixes #3112

.opencode/plugins/ecc-hooks.ts

@@ -16,8 +16,8 @@
 import type { PluginInput } from "@opencode-ai/plugin"
 import * as fs from "fs"
 import * as path from "path"
-import changedFilesTool from "../tools/changed-files.js"
-import dependencyAnalyzerTool from "../tools/dependency-analyzer.js"
+import changedFilesTool from "../tools/changed-files.ts"
+import dependencyAnalyzerTool from "../tools/dependency-analyzer.ts"
 
 /**
  * Type definitions for better type safety
@@ -111,9 +111,9 @@ export const ECCHooksPlugin: ECCHooksPluginFn = async ({
   // This plugin is OpenCode's startup entry point, so a static import
   // failure here previously crashed the whole plugin -- and with it, the
   // entire OpenCode session -- before any hooks could load (see #2530).
-  let changedFilesStore: typeof import("./lib/changed-files-store.js") | undefined
+  let changedFilesStore: typeof import("./lib/changed-files-store.ts") | undefined
   try {
-    const store = await import("./lib/changed-files-store.js")
+    const store = await import("./lib/changed-files-store.ts")
     store.initStore(worktreePath)
     changedFilesStore = store
   } catch {

.opencode/plugins/index.ts

@@ -6,7 +6,7 @@
  * while taking advantage of OpenCode's more sophisticated 20+ event types.
  */
 
-export { ECCHooksPlugin, default } from "./ecc-hooks.js"
+export { ECCHooksPlugin, default } from "./ecc-hooks.ts"
 
 // Re-export for named imports
-export * from "./ecc-hooks.js"
+export * from "./ecc-hooks.ts"