feat(web): align Claude effort options with Claude Code --effort levels (#731)

The Claude effort selector (New Session config + in-session composer) only
offered auto/medium/high/max, missing `low` and `xhigh` — yet `claude --effort`
actually accepts low/medium/high/xhigh/max. Add the two missing levels in both
places so the selector faithfully mirrors the CLI.

Extract the level list + labels into one shared constant
(@hapi/protocol: shared/src/effort.ts, mirroring CLAUDE_MODEL_PRESETS) so the
two UIs derive from a single source and can't drift again. No backend change:
the effort string is free-form end-to-end through to the --effort flag.

ultracode is intentionally excluded — it is a TUI-only /effort session setting,
not an --effort value (the CLI rejects `--effort ultracode`).

shared/src/effort.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, test } from 'bun:test'
+import { CLAUDE_EFFORT_LABELS, CLAUDE_EFFORT_LEVELS } from './effort'
+
+describe('Claude effort constants', () => {
+    test('exposes the Claude Code --effort levels in ascending order', () => {
+        expect(CLAUDE_EFFORT_LEVELS).toEqual(['low', 'medium', 'high', 'xhigh', 'max'])
+    })
+
+    test('every CLAUDE_EFFORT_LEVEL has a label', () => {
+        for (const level of CLAUDE_EFFORT_LEVELS) {
+            expect(CLAUDE_EFFORT_LABELS[level]).toBeDefined()
+        }
+    })
+})

shared/src/effort.ts

@@ -0,0 +1,12 @@
+// Effort levels Claude Code's `--effort` flag accepts, in ascending order.
+// "auto"/null is hapi's sentinel for omitting --effort (model default), not a level here.
+export const CLAUDE_EFFORT_LABELS = {
+    low: 'Low',
+    medium: 'Medium',
+    high: 'High',
+    xhigh: 'XHigh',
+    max: 'Max'
+} as const
+
+export type ClaudeEffortLevel = keyof typeof CLAUDE_EFFORT_LABELS
+export const CLAUDE_EFFORT_LEVELS = Object.keys(CLAUDE_EFFORT_LABELS) as ClaudeEffortLevel[]

shared/src/index.ts

@@ -1,6 +1,7 @@
 export * from './apiTypes'
 export * from './messages'
 export * from './buildInfo'
+export * from './effort'
 export * from './flavors'
 export * from './models'
 export * from './modes'