--source_loras misreads a URL port as the :alpha suffix and refuses to start

Describe the bug

--source_loras rejects a LoRA URL that carries an explicit port, with a misleading "Invalid alpha value" error, and the server fails to start.

The optional :alpha suffix is located with rfind(':') over the whole source string, before the source type is known — src/graph_export/image_generation_graph_cli_parser.cpp:232-245:

// Parse optional :alpha suffix
auto lastColon = source.rfind(':');
if (lastColon != std::string::npos && lastColon > 1) {
    std::string alphaStr = source.substr(lastColon + 1);
    // Skip protocol colons (https:// or http://)
    if (alphaStr.substr(0, 2) != "//") {
        auto alpha = ovms::stof(alphaStr);
        if (!alpha.has_value()) {
            throw std::invalid_argument("Invalid alpha value '" + alphaStr + "' in --source_loras entry: '" + entry + "'");
        }
        ...

The != "//" guard covers the scheme colon of a URL with no port. It does not cover the port colon. For

xray=https://registry.internal:8080/loras/f.safetensors

rfind(':') lands on the port colon, alphaStr becomes 8080/loras/f.safetensors, and ovms::stof rejects it because it requires the whole string to be consumed (src/stringutils.cpp:203-205). The entry is then reported as having an invalid alpha value.

The lastColon > 1 guard correctly protects a Windows drive letter (C:\...), but nothing protects the URL authority component.

Scope: this only affects entries without an explicit alpha suffix. With :0.45 appended, rfind() happens to land on the alpha colon and parsing works, which is presumably why it was not caught — the existing URL tests (UrlLoraWithAlpha, UrlLoraWithoutAlphaPreservesDefault in src/test/lora_graph_export_test.cpp) all use default-port https://huggingface.co/... URLs, as do the CLI cases in src/test/ovmsconfig_test.cpp (:592, :610, :628, :1873) and src/test/pull_hf_model_test.cpp:2586.

To Reproduce

ovms --pull --source_model <sdxl-model> --model_repository_path /tmp/repo \
     --task image_generation \
     --source_loras "xray=https://registry.internal:8080/loras/DD-xray-v1.safetensors"

Result:

Invalid alpha value '8080/loras/DD-xray-v1.safetensors' in --source_loras entry: 'xray=https://registry.internal:8080/loras/DD-xray-v1.safetensors'

Behaviour of the current parsing block across inputs (ovms::stof copied verbatim):

https://huggingface.co/org/repo/resolve/main/f.safetensors   -> OK, no alpha
https://registry.internal:8080/loras/f.safetensors           -> THROW: Invalid alpha value '8080/loras/f.safetensors'
http://localhost:9000/f.safetensors                          -> THROW: Invalid alpha value '9000/f.safetensors'
https://host/f.safetensors:0.8                               -> OK, alpha 0.8
https://registry.internal:8080/loras/f.safetensors:0.45      -> OK, alpha 0.45

Expected behavior

alias=https://host:port/path/file.safetensors is accepted as DIRECT_URL with the default alpha, and alias=https://host:port/path/file.safetensors:0.45 is accepted with alpha 0.45.

Logs

Startup aborts before logging begins; the std::invalid_argument message above is what reaches the console.

Configuration

1. OVMS version: main @ fadb3314
2. --task image_generation, --source_loras pointing at a LoRA served from a host with an explicit port (internal registry, local mirror, localhost:port during testing)
3. CPU
4. N/A
5. Any .safetensors LoRA reachable over a non-default port

Additional context

Suggested fix: restrict the alpha colon to the final path segment — compute source.find_last_of("/\\") and require the colon to fall at or after it. The scheme colon, the port colon and a Windows drive letter all precede the last separator, so all three are excluded structurally instead of by special-casing. The "//" check then becomes unreachable, since nothing after the last separator can contain a path separator.

I have a patch for this and will open a PR shortly.

Start in src/graph_export/image_generation_graph_cli_parser.cpp:232-245 and review the existing URL cases in src/test/lora_graph_export_test.cpp and src/test/ovmsconfig_test.cpp. Add regression coverage for URLs with explicit ports, both without an alpha and with an alpha suffix. Done means both forms are accepted with the expected default or explicit alpha.