fix(desktop): enable Windows mesh-llm builds and address Compute Share startup/MeshLLM debug logging/non-image models trying to parse image input

[stevepresley]

fix: enable Windows mesh-llm desktop builds

Closes #2836
Closes #3300

Summary

• Enable the mesh-llm feature for Windows release and canary desktop builds.
• Bundle required Windows MeshLLM native runtime DLL dependencies as Tauri resources and register their directory at runtime.
• Avoid Windows stack overflows during mesh start and managed-agent start by running heavy startup work on larger-stack OS threads.
• Make Compute Share startup more resilient/idempotent and fix stale progress UI behavior.
• Add opt-in MeshLLM diagnostic logging controls in Compute → Advanced.
• Add relay-mesh protection so prior tool-result images are not replayed into text-only shared-compute LLM requests.

Validation

Validated locally on Windows 11:

• cargo fmt --manifest-path desktop/src-tauri/Cargo.toml --all
• cargo check --manifest-path desktop/src-tauri/Cargo.toml --features mesh-llm
• pnpm typecheck
• cargo check -p buzz-agent
• cargo build -p buzz-agent --release --target x86_64-pc-windows-msvc
• bash scripts/bundle-sidecars.sh x86_64-pc-windows-msvc
• pnpm tauri build --target x86_64-pc-windows-msvc --bundles nsis --features mesh-llm --config "{\"bundle\":{\"createUpdaterArtifacts\":false}}"

Manual validation:

• Installed the NSIS build on Windows 11.
• Verified Settings → Compute no longer shows the mesh-llm feature-stub behavior.
• Verified Compute Share starts and serves requests.
• Verified Windows MeshLLM native runtime dependency loading works with bundled MinGW DLLs.
• Verified managed buzz-agent starts from the installed app.
• Verified relay-mesh LLM calls no longer fail with the text-only model media-input 422 caused by replayed tool-result images.
• Verified MeshLLM diagnostic logging toggle works at runtime.

Related/out of scope findings

Windows relay-mesh validation also reproduced existing ACP/agent delivery behavior where a model may produce Activity/final text without publishing a DM/channel message, and failed ACP turns can be retried later. That is out of scope for this Windows mesh-llm packaging/runtime PR.

Refs #2698
Refs #2421
Refs #2681

[michaelneale]

@stevepresley thanks - that is a big change and not all windows related is it?

[stevepresley]

@stevepresley thanks - that is a big change and not all windows related is it?

It started as mostly Windows related, but these three items are cross-platform.

• Make Compute Share startup more resilient/idempotent and fix stale progress UI behavior.
• Add opt-in MeshLLM diagnostic logging controls in Compute → Advanced.
• Add relay-mesh protection so prior tool-result images are not replayed into text-only shared-compute LLM requests.

I'll update the title

[stevepresley]

@michaelneale opened #3300 to track the 3 other issues fixed in this PR. Let me know if you want me to split it out into a second PR