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/plugin/chat-params.ts

@@ -1,3 +1,5 @@
+import { setProvider } from "../features/hashline-provider-state"
+
 type ChatParamsInput = {
   sessionID: string
   agent: { name?: string }
@@ -66,6 +68,8 @@ export function createChatParamsHandler(args: {
     if (!normalizedInput) return
     if (!isChatParamsOutput(output)) return
 
+    setProvider(normalizedInput.sessionID, normalizedInput.model.providerID)
+
     await args.anthropicEffort?.["chat.params"]?.(normalizedInput, output)
   }
 }

src/plugin/hooks/create-tool-guard-hooks.ts

@@ -10,6 +10,8 @@ import {
   createRulesInjectorHook,
   createTasksTodowriteDisablerHook,
   createWriteExistingFileGuardHook,
+  createHashlineEditDisablerHook,
+  createHashlineReadEnhancerHook,
 } from "../../hooks"
 import {
   getOpenCodeVersion,
@@ -28,6 +30,8 @@ export type ToolGuardHooks = {
   rulesInjector: ReturnType<typeof createRulesInjectorHook> | null
   tasksTodowriteDisabler: ReturnType<typeof createTasksTodowriteDisablerHook> | null
   writeExistingFileGuard: ReturnType<typeof createWriteExistingFileGuardHook> | null
+  hashlineEditDisabler: ReturnType<typeof createHashlineEditDisablerHook> | null
+  hashlineReadEnhancer: ReturnType<typeof createHashlineReadEnhancerHook> | null
 }
 
 export function createToolGuardHooks(args: {
@@ -85,6 +89,14 @@ export function createToolGuardHooks(args: {
     ? safeHook("write-existing-file-guard", () => createWriteExistingFileGuardHook(ctx))
     : null
 
+  const hashlineEditDisabler = isHookEnabled("hashline-edit-disabler")
+    ? safeHook("hashline-edit-disabler", () => createHashlineEditDisablerHook(pluginConfig))
+    : null
+
+  const hashlineReadEnhancer = isHookEnabled("hashline-read-enhancer")
+    ? safeHook("hashline-read-enhancer", () => createHashlineReadEnhancerHook(ctx, { hashline_edit: { enabled: pluginConfig.experimental?.hashline_edit ?? false } }))
+    : null
+
   return {
     commentChecker,
     toolOutputTruncator,
@@ -94,5 +106,7 @@ export function createToolGuardHooks(args: {
     rulesInjector,
     tasksTodowriteDisabler,
     writeExistingFileGuard,
+    hashlineEditDisabler,
+    hashlineReadEnhancer,
   }
 }

src/plugin/tool-execute-after.ts

@@ -43,5 +43,6 @@ export function createToolExecuteAfterHandler(args: {
     await hooks.delegateTaskRetry?.["tool.execute.after"]?.(input, output)
     await hooks.atlasHook?.["tool.execute.after"]?.(input, output)
     await hooks.taskResumeInfo?.["tool.execute.after"]?.(input, output)
+    await hooks.hashlineReadEnhancer?.["tool.execute.after"]?.(input, output)
   }
 }

src/plugin/tool-execute-before.ts

@@ -29,6 +29,7 @@ export function createToolExecuteBeforeHandler(args: {
     await hooks.prometheusMdOnly?.["tool.execute.before"]?.(input, output)
     await hooks.sisyphusJuniorNotepad?.["tool.execute.before"]?.(input, output)
     await hooks.atlasHook?.["tool.execute.before"]?.(input, output)
+    await hooks.hashlineEditDisabler?.["tool.execute.before"]?.(input, output)
 
     if (input.tool === "task") {
       const argsObject = output.args

src/plugin/tool-registry.ts

@@ -25,6 +25,7 @@ import {
   createTaskGetTool,
   createTaskList,
   createTaskUpdateTool,
+  createHashlineEditTool,
 } from "../tools"
 import { getMainSessionID } from "../features/claude-code-session-state"
 import { filterDisabledTools } from "../shared/disabled-tools"
@@ -117,6 +118,11 @@ export function createToolRegistry(args: {
       }
     : {}
 
+  const hashlineEnabled = pluginConfig.experimental?.hashline_edit ?? false
+  const hashlineToolsRecord: Record<string, ToolDefinition> = hashlineEnabled
+    ? { hashline_edit: createHashlineEditTool() }
+    : {}
+
   const allTools: Record<string, ToolDefinition> = {
     ...builtinTools,
     ...createGrepTools(ctx),
@@ -132,6 +138,7 @@ export function createToolRegistry(args: {
     slashcommand: slashcommandTool,
     interactive_bash,
     ...taskToolsRecord,
+    ...hashlineToolsRecord,
   }
 
   const filteredTools = filterDisabledTools(allTools, pluginConfig.disabled_tools)