feat(gateway): adapt Claude Haiku 5.5

Closes #7919. Wire claude-haiku-5-5 (released 2026-10-07) across model
registry, effort catalog, pricing, billing, validation and Codex
descriptors, following the opus-5-5/sonnet-5-5 template and the official
migration guide + overview specs.

- registry: DefaultModels entry (fixed ID, no date suffix per guide)
- effort: full low/medium/high/xhigh/max family + IsHaiku55 +
  claude-haiku-5.5 dotted normalization (official default: medium)
- pricing catalog: 1M/128k limits, base (<=100k) prices and
  *_above_100k_tokens absolute prices; the existing ladder derivation
  yields threshold=100000 with uniform 5x multipliers, matching the
  official two-tier table exactly (cache tiers follow input x5)
- billing/pricing fallbacks carry the same tier so a missing catalog
  entry can never silently bill >100k prompts at base rate
- validation: adaptive-only thinking (enabled always 400; disabled 400
  at xhigh/max), sonnet-style sampling locks, temp+top_p combo rejected,
  forced tool_choice explicitly allowed (differs from opus/sonnet)
- oauth mimicry: skip temperature:1 top-up when top_p is present on
  sampling-locked models (sonnet-5-5 included), otherwise the gateway
  manufactures the temp+top_p 400 itself
- toolset beta filter + Codex 1M context cover haiku-5-5
- Bedrock/Antigravity mappings intentionally left out (no 5.5 entries
  exist there at all, same as opus-5-5); Vertex passes the fixed ID
  through untouched

backend/resources/model-pricing/model_prices_and_context_window.json

@@ -381,6 +381,40 @@
     "supports_tool_choice": true,
     "supports_vision": true
   },
+  "claude-haiku-5-5": {
+    "cache_creation_input_token_cost": 1.25e-07,
+    "cache_creation_input_token_cost_above_1hr": 2e-07,
+    "cache_creation_input_token_cost_above_100k_tokens": 6.25e-07,
+    "cache_creation_input_token_cost_above_1hr_above_100k_tokens": 1e-06,
+    "cache_read_input_token_cost": 1e-08,
+    "cache_read_input_token_cost_above_100k_tokens": 5e-08,
+    "input_cost_per_token": 1e-07,
+    "input_cost_per_token_above_100k_tokens": 5e-07,
+    "litellm_provider": "anthropic",
+    "max_input_tokens": 1000000,
+    "max_output_tokens": 128000,
+    "max_tokens": 128000,
+    "mode": "chat",
+    "output_cost_per_token": 5e-07,
+    "output_cost_per_token_above_100k_tokens": 2.5e-06,
+    "source": "https://platform.claude.com/docs/en/models/haiku-5-5/overview",
+    "supports_adaptive_thinking": true,
+    "supports_assistant_prefill": false,
+    "supports_computer_use": true,
+    "supports_function_calling": true,
+    "supports_max_reasoning_effort": true,
+    "supports_output_config": true,
+    "supports_pdf_input": true,
+    "supports_prompt_caching": true,
+    "supports_reasoning": true,
+    "supports_response_schema": true,
+    "supports_sampling_params": false,
+    "supports_tool_choice": true,
+    "supports_vision": true,
+    "supports_xhigh_reasoning_effort": true,
+    "input_cost_per_token_batches": 5e-08,
+    "output_cost_per_token_batches": 2.5e-07
+  },
   "claude-opus-4-1": {
     "cache_creation_input_token_cost": 1.875e-05,
     "cache_creation_input_token_cost_above_1hr": 3e-05,