feat: Claude Code CLI v2.1.105–v2.1.131 support (#274)

## Overview

Full audit and implementation of Claude Code CLI changelog entries from v2.1.105 through v2.1.131.

## Changes

### Implemented

- **#268** — Add `claude-opus-4-7` to the model picker, update all model pricing and context window sizes (also fixes a bug where `claude-opus-4-6` was coded as 200K context instead of 1M)
- **#269** — Expose effort level setting in UI via `--effort <level>` flag (`low`, `medium`, `high`, `xhigh`, `max`)
- **#273** — Expose prompt caching TTL env vars in UI (`ENABLE_PROMPT_CACHING_1H` / `FORCE_PROMPT_CACHING_5M`)
- **#267** — Add `PreCompact` hook support — emits `claude:pre-compact` event with "Compacting context..." toast and thinking state
- **#270** — Parse `plugin_errors` from stream-json init event and surface them as error output lines
- **#266** — Bump supported CLI version constant to `2.1.131`

### Closed as Not Applicable

- **#271** (`autoScrollEnabled`) — TUI-only setting; we manage our own scroll behaviour
- **#272** (`tui` fullscreen mode) — TUI-only setting; we use stream-json and never activate the TUI

## Testing

All checks pass (`./check-all.sh`) including frontend lint, format, type check, Vitest coverage, Clippy, and Rust test coverage.

✨ This PR was created with help from Hikari~ 🌸

Reviewed-on: #274
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

src/lib/stores/config.ts

@@ -99,6 +99,10 @@ export interface HikariConfig {
   show_clear_context_on_plan_accept: boolean;
   // Custom model option env var (v2.1.81+)
   custom_model_option: string | null;
+  // Effort level for Claude Code (v2.1.111+) — null means use CLI default
+  effort_level: string | null;
+  // Prompt caching TTL override (v2.1.108+) — null means use CLI default
+  prompt_caching_ttl: string | null;
 }
 
 const defaultConfig: HikariConfig = {
@@ -161,6 +165,8 @@ const defaultConfig: HikariConfig = {
   bare_mode: false,
   show_clear_context_on_plan_accept: true,
   custom_model_option: null,
+  effort_level: null,
+  prompt_caching_ttl: null,
 };
 
 function createConfigStore() {