[BUG] /pr-comments uses wrong model id when used with Google Vertex AI

Environment

• Platform (select one):
• [ ] Anthropic API
• [ ] AWS Bedrock
• [x] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.67
• Operating System: macOS Sequoia (15.5), aarch64
• Terminal: Ghostty

Bug Description

/pr-comments uses wrong model id when used with Google Vertex AI.

 ⎿ API Error: 404 {"error":{"code":404,"message":"Publisher Model
    `projects/project_id_xxx/locations/europe-west1/publishers/anthropic/models/claude-3-5-haiku-20241022` not found.","status":"NOT_FOUND"}}

Steps to Reproduce

1. Run CLAUDE_CODE_USE_VERTEX=1 claude
2. Type /pr-comments

Expected Behaviour

Comments from the PR are pulled into the current context window

Actual Behaviour

 ⎿ API Error: 404 {"error":{"code":404,"message":"Publisher Model
    `projects/project_id_xxx/locations/europe-west1/publishers/anthropic/models/claude-3-5-haiku-20241022` not found.","status":"NOT_FOUND"}}

Extra Claude Environments Variables

Following environments variables might be handy for debugging, albeit not necessary.

$env.ANTHROPIC_MODEL = 'claude-sonnet-4@20250514'
$env.ANTHROPIC_SMALL_FAST_MODEL = 'claude-3-5-haiku@20241022'
$env.CLOUD_ML_REGION = 'europe-west1'
$env.VERTEX_REGION_CLAUDE_4_0_SONNET = "europe-west1"
$env.VERTEX_REGION_CLAUDE_3_5_HAIKU = "europe-west1"

Relates to #4252 #4264