refactor(hashline): override native edit tool instead of separate tool + disabler hook

Replace 3-component hashline system (separate hashline_edit tool + edit
disabler hook + OpenAI-exempted read enhancer) with 2-component system
that directly overrides the native edit tool key, matching the
delegate_task pattern.

- Register hashline tool as 'edit' key to override native edit
- Delete hashline-edit-disabler hook (no longer needed)
- Delete hashline-provider-state module (no remaining consumers)
- Remove OpenAI exemption from read enhancer (explicit opt-in means all providers)
- Remove setProvider wiring from chat-params

src/plugin/tool-execute-before.ts

@@ -29,8 +29,6 @@ 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
       const category = typeof argsObject.category === "string" ? argsObject.category : undefined