[v6.0] fix: more precise default message for tool execution denial

[gr2m]

Backport of #14656 to release-v6.0. Changes the default tool call denial message from 'Tool execution denied.' to the more precise 'Tool call execution denied.' across the provider message converters, so that GPT-5 models do not refuse further calls to the same tool with different inputs. Conflict resolution adaptations: in packages/ai/src/ui/convert-to-model-messages.ts v6's toolPart.approval?.reason optional chaining was kept (main uses toolPart.approval.reason); in packages/openai/src/responses/convert-to-openai-responses-input.test.ts the new execution-denied custom tool test was inserted alongside v6's existing aliased-tool-name test; the google change landed in v6's convert-to-google-generative-ai-messages.ts (renamed to convert-to-google-messages.ts on main); and the inline snapshot in packages/ai/src/ui/convert-to-model-messages.test.ts (not touched by the original commit) was updated to the new default message. Part of the v6.0 backport tracking issue #16767.

[github-actions]

⚠️ Backport to release-v5.0 created but has conflicts: #16835

[github-actions]

🚀 Published in:

Package	Version
ai	6.0.221 github npm
@ai-sdk/alibaba	1.0.36 github npm
@ai-sdk/amazon-bedrock	4.0.131 github npm
@ai-sdk/angular	2.0.222 github npm
@ai-sdk/anthropic	3.0.95 github npm
@ai-sdk/anthropic-aws	1.0.17 github npm
@ai-sdk/assemblyai	2.0.44 github npm
@ai-sdk/azure	3.0.86 github npm
@ai-sdk/baseten	1.0.61 github npm
@ai-sdk/black-forest-labs	1.0.45 github npm
@ai-sdk/bytedance	1.0.25 github npm
@ai-sdk/cerebras	2.0.64 github npm
@ai-sdk/cohere	3.0.46 github npm
@ai-sdk/deepgram	2.0.43 github npm
@ai-sdk/deepinfra	2.0.62 github npm
@ai-sdk/deepseek	2.0.46 github npm
@ai-sdk/elevenlabs	2.0.43 github npm
@ai-sdk/fal	2.0.44 github npm
@ai-sdk/fireworks	2.0.66 github npm
@ai-sdk/gateway	3.0.145 github npm
@ai-sdk/gladia	2.0.43 github npm
@ai-sdk/google	3.0.90 github npm
@ai-sdk/google-vertex	4.0.158 github npm
@ai-sdk/groq	3.0.49 github npm
@ai-sdk/huggingface	1.0.60 github npm
@ai-sdk/hume	2.0.43 github npm
@ai-sdk/klingai	3.0.28 github npm
@ai-sdk/langchain	2.0.229 github npm
@ai-sdk/llamaindex	2.0.221 github npm
@ai-sdk/lmnt	2.0.43 github npm
@ai-sdk/luma	2.0.43 github npm
@ai-sdk/mcp	1.0.60 github npm
@ai-sdk/mistral	3.0.47 github npm
@ai-sdk/moonshotai	2.0.34 github npm
@ai-sdk/open-responses	1.0.26 github npm
@ai-sdk/openai	3.0.82 github npm
@ai-sdk/openai-compatible	2.0.58 github npm
@ai-sdk/perplexity	3.0.44 github npm
@ai-sdk/prodia	1.0.42 github npm
@ai-sdk/provider-utils	4.0.37 github npm
@ai-sdk/quiverai	1.0.10 github npm
@ai-sdk/react	3.0.223 github npm
@ai-sdk/replicate	2.0.43 github npm
@ai-sdk/revai	2.0.43 github npm
@ai-sdk/rsc	2.0.221 github npm
@ai-sdk/svelte	4.0.221 github npm
@ai-sdk/togetherai	2.0.63 github npm
@ai-sdk/valibot	2.0.38 github npm
@ai-sdk/vercel	2.0.60 github npm
@ai-sdk/voyage	1.0.14 github npm
@ai-sdk/vue	3.0.221 github npm
@ai-sdk/xai	3.0.104 github npm