Add new models

[atdrendel]

• Add Devstral and Ministral
• Add Nemotron
• Add Qwen3.5
• Append assistant tool calls to transcripts to fix tool calling

[Copilot]

Pull request overview

This PR expands SHLLM’s model surface area (Devstral/Ministral, Nemotron, Qwen3.5) and adjusts parsing + transcript construction to support multi-step tool workflows more reliably.

Changes:

• Add new model wrappers + response parsers for Mistral3VLM (Devstral/Ministral), NemotronHModel, and Qwen3.5 (incl. MoE).
• Update tool-workflow tests to append assistant tool-call messages into transcripts before appending tool results.
• Bump MLX Swift LM dependency and switch swift-transformers to the shareup fork.

Reviewed changes

Copilot reviewed 20 out of 22 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
bin/download.sh	Adds new model IDs for download helper script.
Tests/SHLLMTests/Models/Qwen3_5-9BTests.swift	New test suite for Qwen3.5-9B (streaming/awaiting/tools/VLM).
Tests/SHLLMTests/Models/Qwen3_5-35B-A3BTests.swift	New test suite for Qwen3.5-35B-A3B (MoE) workflows.
Tests/SHLLMTests/Models/Qwen3_5-2BTests.swift	New test suite for Qwen3.5-2B including thinking on/off behavior.
Tests/SHLLMTests/Models/Qwen3_5-27BTests.swift	New test suite for Qwen3.5-27B workflows.
Tests/SHLLMTests/Models/Qwen3-8BTests.swift	Ensures assistant tool calls are appended before tool results in tool workflows.
Tests/SHLLMTests/Models/Qwen3-4BTests.swift	Same transcript fix for Qwen3-4B tool workflows.
Tests/SHLLMTests/Models/Qwen3-30BTests.swift	Same transcript fix for Qwen3-30B tool workflows.
Tests/SHLLMTests/Models/Orchestrator-8BTests.swift	Same transcript fix for Orchestrator tool workflows (tests remain disabled where applicable).
Tests/SHLLMTests/Models/NemotronNano-30BTests.swift	New test suite for Nemotron Nano tool workflows.
Tests/SHLLMTests/Models/Ministral-3-14BTests.swift	New test suite for Ministral-3-14B including VLM extraction.
Tests/SHLLMTests/Models/LFM2-8B-A1BTests.swift	Appends assistant tool calls and re-enables multi-tool workflow test.
Tests/SHLLMTests/Models/Devstral2Small-24BTests.swift	New test suite for Devstral2 Small 24B (Mistral3VLM).
Tests/SHLLMTests/Helpers.swift	Minor wording tweak in image input system prompt.
Tests/SHLLMTests/HarmonyTests.swift	Adds missing MLXLMCommon import (ToolCall usage).
Sources/SHLLM/UserInput+SHLLM.swift	Adds appendAssistantToolCall and changes generic tool-result message content to JSON string.
Sources/SHLLM/ThinkingTagProcessor.swift	Adds documentation clarifying parsing modes.
Sources/SHLLM/SHLLM.swift	Re-exports new model types (Mistral3TextModel, NemotronHModel, Mistral3VLM, Qwen35, Qwen35MoE).
Sources/SHLLM/ResponseParser.swift	Adds parsers for Qwen3.5, Nemotron, Mistral3VLM (and shared Qwen3.5 parser selection).
Sources/SHLLM/LLM.swift	Adds new model constructors + resource directory helpers for Devstral2/Ministral/Nemotron/Qwen3.5.
Package.swift	Bumps mlx-swift-lm and switches swift-transformers dependency source/version.
Package.resolved	Updates resolved graph to match new dependency versions/sources.

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