### What problem does this PR solve?
```
RAGFlow(user)> embed text 'what is rag' 'who are you' with 'embedding-3@test@zhipu-ai' dimension 16;
+-----------+-------+
| dimension | index |
+-----------+-------+
| 16 | 0 |
| 16 | 1 |
+-----------+-------+
RAGFlow(user)> rerank query 'what is rag' document 'rag is retrieval augment generation' 'rag need llm' 'famous rag project includes ragflow' with 'rerank@test@zhipu-ai' top 2;
+-------+-----------------+
| index | relevance_score |
+-------+-----------------+
| 0 | 1 |
| 2 | 0.99999976 |
+-------+-----------------+
```
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
Signed-off-by: Jin Hai <haijin.chn@gmail.com>
### What problem does this PR solve?
The NVIDIA Go driver added in #14623 has a real chat path, but
\`ListModels\` and \`CheckConnection\` are stubs that always return \`no
such method\`. So:
- The model picker cannot auto-populate available NVIDIA NIM model ids.
Users have to type the full id by hand (e.g.
\`abacusai/dracarys-llama-3.1-70b-instruct\`).
- The "Check connection" button always fails for NVIDIA, even when the
base URL is reachable and the API key is accepted.
NVIDIA NIM is OpenAI-compatible. \`/v1/models\` works with the same
Bearer token used for chat. The
\`conf/models/nvidia.json\` file already wires the \`models\`
url_suffix, so no config change is needed.
### What this PR includes
- \`internal/entity/models/nvidia.go\`:
- \`ListModels\` now calls
\`GET ${BaseURL}/${URLSuffix.Models}\`, parses
\`response.data[*].id\`, and returns the list. Same shape
as the moonshot, xai, and openai drivers.
- \`CheckConnection\` now calls \`ListModels\` and returns its
error. Same pattern xai, moonshot, deepseek, aliyun, and
gitee already use.
\`Balance\`, \`Encode\`, and \`Rerank\` are still stubs in this PR and
can be added in follow-ups.
No JSON change. No factory change. No interface change.
### How the implementation works
- Region resolution falls back to \`default\` when the supplied region
is unknown, so a stray region value does not break a valid request.
- The Authorization header is only set when \`apiConfig\` and \`ApiKey\`
are non-nil and non-empty. This avoids a nil-pointer dereference and
lets self-hosted NIM deployments without a key still work.
- Non-200 responses propagate the upstream status line and body so the
user sees a real error message.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
### How was this tested?
- \`go build ./internal/entity/models/...\` in a clean go 1.25 image
(the go.mod minimum) returns exit 0.
- The full method set on \`NvidiaModel\` still matches the
\`ModelDriver\` interface.
- Pattern parity with the existing xai, moonshot, deepseek, aliyun,
gitee, and openai drivers.
Closes#14635
### What problem does this PR solve?
1. **Implement `OpenRouter` Provider:** Fully support OpenRouter AI
models (e.g., `gemma`, `minimax`). Includes robust handling of
Server-Sent Events (SSE) streams, error event interception, and proper
parsing of both `reasoning_content` and standard `content`.
2. **Fix BaseURL Resolution Bug:** Fixed a critical edge case in region
configuration parsing. Added a strict empty string check
(`*apiConfig.Region != ""`) alongside the `nil` check. This ensures that
if the UI passes an empty string, the system correctly falls back to the
`"default"` region, preventing `unsupported protocol scheme ""` errors
during HTTP requests.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
1. **Implement `Nvidia` Provider:** Fully support NVIDIA NIM APIs with
robust parameter handling (including the `thinking` parameter) and safe
URL merging in `NewInstance`.
2. **Fix Misleading CLI Errors:** Corrected a bug in `common_command.go`
where failed chat requests inaccurately reported `failed to list
instance models`.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
