refactor: route raw Bun.file/write/hash/which/spawn through runtime shims

Eliminates 19 unguarded `Bun.*` runtime call sites in the plugin bundle
that crashed with `ReferenceError: Bun is not defined` under Electron.

Per-tool-call hot paths (executed on every Read/Edit):
- src/tools/hashline-edit/hash-computation.ts: Bun.hash.xxHash32 → bunHashXxh32
- src/tools/hashline-edit/hashline-edit-executor.ts: 8 sites via bunFile/bunWrite
- src/hooks/hashline-read-enhancer/hook.ts: Bun.file → bunFile
- src/hooks/hashline-edit-diff-enhancer/hook.ts: 2 sites via bunFile

Plugin-load paths:
- src/hooks/claude-code-hooks/config.ts and config-loader.ts: Bun.file → bunFile
- src/features/claude-code-mcp-loader/loader.ts: Bun.file → bunFile
- src/features/claude-code-plugin-loader/mcp-server-loader.ts: Bun.file → bunFile
- src/features/team-mode/deps.ts: Bun.spawn → spawn shim
- src/hooks/session-notification-utils.ts: Bun.which → bunWhich, also drops
  the bare `declare const Bun` ambient declaration
- src/shared/binary-downloader.ts: Bun.write → bunWrite

Pure mechanical API swaps. No control-flow or signature changes.

src/hooks/claude-code-hooks/config-loader.ts

@@ -3,6 +3,7 @@ import { join } from "path"
 import type { ClaudeHookEvent } from "./types"
 import { log } from "../../shared/logger"
 import { getOpenCodeConfigDir } from "../../shared"
+import { bunFile } from "../../shared/bun-file-shim"
 
 const CONFIG_CACHE_TTL_MS = 30_000
 
@@ -61,7 +62,7 @@ async function loadConfigFromPath(path: string): Promise<PluginExtendedConfig |
   }
 
   try {
-    const content = await Bun.file(path).text()
+    const content = await bunFile(path).text()
     return JSON.parse(content) as PluginExtendedConfig
   } catch (error) {
     log("Failed to load config", { path, error })

src/hooks/claude-code-hooks/config.ts

@@ -1,6 +1,7 @@
 import { join } from "path"
 import { existsSync } from "fs"
 import { getClaudeConfigDir } from "../../shared"
+import { bunFile } from "../../shared/bun-file-shim"
 import type { ClaudeHooksConfig, HookMatcher, HookAction } from "./types"
 
 const CONFIG_CACHE_TTL_MS = 30_000
@@ -126,7 +127,7 @@ export async function loadClaudeHooksConfig(
   for (const settingsPath of paths) {
     if (existsSync(settingsPath)) {
       try {
-        const content = await Bun.file(settingsPath).text()
+        const content = await bunFile(settingsPath).text()
         const settings = JSON.parse(content) as { hooks?: RawClaudeHooksConfig }
         if (settings.hooks) {
           const normalizedHooks = normalizeHooksConfig(settings.hooks)

src/hooks/hashline-edit-diff-enhancer/hook.ts

@@ -1,4 +1,5 @@
 import { log } from "../../shared"
+import { bunFile } from "../../shared/bun-file-shim"
 import { generateUnifiedDiff, countLineDiffs } from "../../tools/hashline-edit/diff-utils"
 
 interface HashlineEditDiffEnhancerConfig {
@@ -38,7 +39,7 @@ function extractFilePath(args: Record<string, unknown>): string | undefined {
 
 async function captureOldContent(filePath: string): Promise<string> {
 	try {
-		const file = Bun.file(filePath)
+		const file = bunFile(filePath)
 		if (await file.exists()) {
 			return await file.text()
 		}
@@ -79,7 +80,7 @@ export function createHashlineEditDiffEnhancerHook(config: HashlineEditDiffEnhan
 
 			let newContent: string
 			try {
-				newContent = await Bun.file(filePath).text()
+				newContent = await bunFile(filePath).text()
 			} catch {
 				log("[hashline-edit-diff-enhancer] failed to read new content", { filePath })
 				return

src/hooks/hashline-read-enhancer/hook.ts

@@ -1,4 +1,5 @@
 import type { PluginInput } from "@opencode-ai/plugin"
+import { bunFile } from "../../shared/bun-file-shim"
 import { computeLineHash } from "../../tools/hashline-edit/hash-computation"
 
 const WRITE_SUCCESS_MARKER = "File written successfully."
@@ -178,7 +179,7 @@ async function appendWriteHashlineOutput(output: { output: string; metadata: unk
     return
   }
 
-  const file = Bun.file(filePath)
+  const file = bunFile(filePath)
   if (!(await file.exists())) {
     return
   }

src/hooks/session-notification-utils.ts

@@ -1,14 +1,11 @@
 import { log } from "../shared/logger"
-
-declare const Bun: {
-  which(commandName: string): string | null
-}
+import { bunWhich } from "../shared/bun-which-shim"
 
 type Platform = "darwin" | "linux" | "win32" | "unsupported"
 
 async function findCommand(commandName: string): Promise<string | null> {
   try {
-    return Bun.which(commandName)
+    return bunWhich(commandName)
   } catch (error) {
     log("[session-notification] failed to resolve command path", {
       commandName,