refactor(deps): rename ragflow_deps directory to deps (#21345)

## Summary

Rename the repository dependency-resource directory `ragflow_deps/` to
`deps/`, and update every hardcoded reference to that directory name so
the rename does not break resource loading at build/runtime.

This is not a purely cosmetic rename: the Go runtime hardcodes the
directory name as a resource search path (e.g.
`internal/common/model_assets.go` trimming the `deps/` prefix, and the
tokenizers joining `deps/` into candidate paths), and the Dockerfiles
copy assets into `/ragflow/deps`. Those literals must move together with
the directory, otherwise assets fail to resolve.

## Two intentional exceptions (kept unchanged)

The rename deliberately keeps two names that only *coincidentally*
contained the old string:

- The published image tag `infiniflow/ragflow_deps:latest` (used by
`Dockerfile`, `Dockerfile_base`, docs, and CI `image inspect` checks).
- The CI install path `/opt/ragflow_deps` inside the CI runner image
(`build.sh` `SYSTEM_DEPS_TOKENIZER`).

## Changes

- `git mv ragflow_deps deps`.
- `build.sh`: `CL100K_TABLE_RELPATH`, native asset zip path, and related
references updated to `deps/`.
- `tools/scripts/download_dev_deps.py`: `RAGFLOW_DEPS_DIR` points at
`deps/`.
- Go runtime resource search paths (`internal/common`,
`internal/tokenizer`) updated to the `deps/` layout.
- `Dockerfile` / `Dockerfile_base`: container asset path changed to
`/ragflow/deps`; kept tag `infiniflow/ragflow_deps:latest` unchanged.
- Docs / `AGENTS.md` / CI workflow paths updated to the new directory
name.

## Test plan

- Go unit tests in `internal/common` and `internal/tokenizer` updated to
the new `deps/` layout and pass via `bash build.sh --test`.
- Python download scripts import and build URLs correctly (`py_compile`
clean).
- Added `tools/scripts/test_dep_rename_invariants.py` as a regression
guard asserting the two intentional exceptions (`/opt/ragflow_deps` and
`infiniflow/ragflow_deps`) stay intact, so a future blanket rename
cannot silently regress them.

---

## Follow-up fix (commit 2f6857095d)

The original rename used a blanket `sed s/ragflow_deps/deps/g` and only
selectively reverted `build.sh`. That left two intentionally-kept names
rewritten, which this follow-up restores:

- CI install path `/opt/ragflow_deps` — `sep-tests.yml` had been changed
to read `/opt/deps`, breaking the offline cl100k table fallback (the
cached-image path pointed at a directory that never receives the file).
Restored to `/opt/ragflow_deps`.
- Published image tag `infiniflow/ragflow_deps` — left as bare
`infiniflow/deps` in `sep-tests.yml` comments/echo, `.dockerignore`, and
`Dockerfile` / `Dockerfile_base` error messages. Restored to
`infiniflow/ragflow_deps`.

The regression guard `tools/scripts/test_dep_rename_invariants.py` was
added to prevent recurrence.

README_ko.md

@@ -223,10 +223,10 @@ Docker는 빠른 평가, 통합 테스트 및 프로덕션에 적합하고 소
 
    ```bash
    uv run tools/scripts/download_dev_deps.py
-   uv run ragflow_deps/download_deps.py
+   uv run deps/download_deps.py
    ```
 
-   `download_dev_deps.py`는 pdfium, pdf_oxide, office_oxide, onnxruntime을 `~/ragflow-native-libs`에 내려받아 압축 해제합니다. `download_deps.py`는 cl100k 어휘집, DeepDoc 모델, 임베딩 토크나이저 리소스를 `ragflow_deps/`에 내려받습니다. 두 스크립트 모두 Python 스크립트이며, `uv run`이 선언된 종속성(`requests`, 모델 및 토크나이저 다운로드에는 `huggingface-hub` 추가)을 자동으로 설치합니다. 같은 리소스를 다른 방법으로 준비했다면 이 단계를 건너뛰세요. 저장소 루트에서 시작하면 Go 서비스가 `internal/rag/res/deepdoc`을 자동으로 찾습니다. 다른 디렉터리에서 시작하려면 `DEEPDOC_MODEL_DIR`을 해당 디렉터리의 절대 경로로 설정하세요.
+   `download_dev_deps.py`는 pdfium, pdf_oxide, office_oxide, onnxruntime을 `~/ragflow-native-libs`에 내려받아 압축 해제합니다. `download_deps.py`는 cl100k 어휘집, DeepDoc 모델, 임베딩 토크나이저 리소스를 `deps/`에 내려받습니다. 두 스크립트 모두 Python 스크립트이며, `uv run`이 선언된 종속성(`requests`, 모델 및 토크나이저 다운로드에는 `huggingface-hub` 추가)을 자동으로 설치합니다. 같은 리소스를 다른 방법으로 준비했다면 이 단계를 건너뛰세요. 저장소 루트에서 시작하면 Go 서비스가 `internal/rag/res/deepdoc`을 자동으로 찾습니다. 다른 디렉터리에서 시작하려면 `DEEPDOC_MODEL_DIR`을 해당 디렉터리의 절대 경로로 설정하세요.
 
 3. 서비스를 빌드합니다: