feat(snowflake-cortex): add Claude Opus 5, Sonnet 5, Opus 4.6 and Opus 4.5 (#4417)

* feat(snowflake-cortex): add Claude Opus 5, Sonnet 5, Opus 4.6 and Opus 4.5

* fix(snowflake-cortex): align Claude reasoning_options with tested chat-completions surface

Verified against POST /api/v2/cortex/v1/chat/completions:

- Opus 5 / Sonnet 5: reasoning.effort and reasoning.max_tokens return 400.
  reasoning_effort, output_config.effort and thinking.type return 200 but are
  ignored (reasoning_effort=bogus_zzz also returns 200) and never produce
  reasoning_details, so no caller control is exposed -> [].
- Opus 4.6 / 4.5: reasoning.max_tokens is the only field that actually engages
  thinking (sole case returning reasoning_details) -> budget_tokens. Effort
  values are not read (effort=bogus_zzz behaves identically), and max_tokens=100
  is accepted, so no effort enum and no min bound.

providers/snowflake-cortex/models/claude-opus-4-5.toml

@@ -0,0 +1,3 @@
+base_model = "anthropic/claude-opus-4-5"
+
+reasoning_options = [{ type = "budget_tokens" }]

providers/snowflake-cortex/models/claude-opus-4-6.toml

@@ -0,0 +1,3 @@
+base_model = "anthropic/claude-opus-4-6"
+
+reasoning_options = [{ type = "budget_tokens" }]

providers/snowflake-cortex/models/claude-opus-5.toml

@@ -0,0 +1,3 @@
+base_model = "anthropic/claude-opus-5"
+
+reasoning_options = []

providers/snowflake-cortex/models/claude-sonnet-5.toml

@@ -0,0 +1,3 @@
+base_model = "anthropic/claude-sonnet-5"
+
+reasoning_options = []