feat(hashline): port hashline edit tool from oh-my-pi

This PR ports the hashline edit tool from oh-my-pi to oh-my-opencode as an experimental feature.

## Features
- New experimental.hashline_edit config flag
- hashline_edit tool with 4 operations: set_line, replace_lines, insert_after, replace
- Hash-based line anchors for safe concurrent editing
- Edit tool disabler for non-OpenAI providers
- Read output enhancer with LINE:HASH prefixes
- Provider state tracking module

## Technical Details
- xxHash32-based 2-char hex hashes
- Bottom-up edit application to prevent index shifting
- OpenAI provider exemption (uses native apply_patch)
- 90 tests covering all operations and edge cases
- All files under 200 LOC limit

## Files Added/Modified
- src/tools/hashline-edit/ (7 files, ~400 LOC)
- src/hooks/hashline-edit-disabler/ (4 files, ~200 LOC)
- src/hooks/hashline-read-enhancer/ (3 files, ~400 LOC)
- src/features/hashline-provider-state.ts (13 LOC)
- src/config/schema/experimental.ts (hashline_edit flag)
- src/config/schema/hooks.ts (2 new hook names)
- src/plugin/tool-registry.ts (conditional registration)
- src/plugin/chat-params.ts (provider state tracking)
- src/tools/index.ts (export)
- src/hooks/index.ts (exports)

src/cli/run/integration.test.ts

@@ -1,9 +1,11 @@
-import { describe, it, expect, mock, spyOn, beforeEach, afterEach } from "bun:test"
+import { describe, it, expect, mock, spyOn, beforeEach, afterEach, afterAll } from "bun:test"
 import type { RunResult } from "./types"
 import { createJsonOutputManager } from "./json-output"
 import { resolveSession } from "./session-resolver"
 import { executeOnCompleteHook } from "./on-complete-hook"
 import type { OpencodeClient } from "./types"
+import * as originalSdk from "@opencode-ai/sdk"
+import * as originalPortUtils from "../../shared/port-utils"
 
 const mockServerClose = mock(() => {})
 const mockCreateOpencode = mock(() =>
@@ -27,6 +29,11 @@ mock.module("../../shared/port-utils", () => ({
   DEFAULT_SERVER_PORT: 4096,
 }))
 
+afterAll(() => {
+  mock.module("@opencode-ai/sdk", () => originalSdk)
+  mock.module("../../shared/port-utils", () => originalPortUtils)
+})
+
 const { createServerConnection } = await import("./server-connection")
 
 interface MockWriteStream {

src/cli/run/server-connection.test.ts

@@ -1,4 +1,7 @@
-import { describe, it, expect, mock, beforeEach, afterEach } from "bun:test"
+import { describe, it, expect, mock, beforeEach, afterEach, afterAll } from "bun:test"
+
+import * as originalSdk from "@opencode-ai/sdk"
+import * as originalPortUtils from "../../shared/port-utils"
 
 const originalConsole = globalThis.console
 
@@ -25,6 +28,11 @@ mock.module("../../shared/port-utils", () => ({
   DEFAULT_SERVER_PORT: 4096,
 }))
 
+afterAll(() => {
+  mock.module("@opencode-ai/sdk", () => originalSdk)
+  mock.module("../../shared/port-utils", () => originalPortUtils)
+})
+
 const { createServerConnection } = await import("./server-connection")
 
 describe("createServerConnection", () => {