fix(messages): preserve Claude 4.x version suffix so vision routes to the right model

[dsgn93-creator]

Problem

Vision requests through --claude-code mode fail with an internal server error on Copilot Enterprise even though:

• copilot-vision-request: true is correctly added by create-chat-completions.ts when an image_url part is detected
• The Anthropic image block is correctly translated to OpenAI image_url with a base64 data URI in mapContent
• The user's plan (Enterprise) and target model (Opus 4.7) both support vision

The failure is in translateModelName. Copilot lists its Claude models as dot-versioned:

claude-opus-4.7
claude-opus-4.6
claude-sonnet-4.6

…but Claude Code sends dash-versioned IDs with a date suffix, e.g. claude-opus-4-7-20251030. The current regex:

if (model.startsWith("claude-opus-")) {
  return model.replace(/^claude-opus-4-.*/, "claude-opus-4")
}

…rewrites that to plain claude-opus-4, which (a) loses the 4.5/4.6/4.7 capability tier and (b) routes vision-bearing requests to a fallback model that does not have vision enabled — producing the internal server error.

Repro: send any image via Claude Code → 500 from Copilot. Text-only requests succeed because Copilot is forgiving about unknown model aliases for non-vision payloads.

Fix

Match claude-(opus|sonnet|haiku)-N-M(-YYYYMMDD)? and convert dash → dot, producing the actual model ID Copilot exposes (claude-opus-4.7). Legacy fallbacks remain unchanged for any shape that doesn't match.

const versioned = model.match(
  /^claude-(opus|sonnet|haiku)-(\d+)-(\d+)(?:-\d{6,8})?$/,
)
if (versioned) {
  return `claude-${versioned[1]}-${versioned[2]}.${versioned[3]}`
}

Verification

claude-opus-4-7-20251030    -> claude-opus-4.7   ✅
claude-opus-4-6-20250901    -> claude-opus-4.6   ✅
claude-sonnet-4-6-20250901  -> claude-sonnet-4.6 ✅
claude-opus-4-1-20250805    -> claude-opus-4.1   ✅
claude-opus-4               -> claude-opus-4     (legacy, unchanged)
claude-3-5-sonnet-20241022  -> claude-3-5-sonnet-20241022 (passthrough)

After patching locally and reinstalling, vision requests through --claude-code now succeed because Copilot routes them to the actual Opus 4.7 endpoint instead of the unknown-alias fallback.

Related: #16, #36, #60 (all touched the vision pipeline but none addressed the model-name rewriting).