ci: avoid unnecessary dep installs in lint targets (#36046)

CI lint jobs use `uv run --all-groups` for all tools, but ruff doesn't
need dependency resolution — only mypy does. By splitting into
`UV_RUN_LINT` (ruff) and `UV_RUN_TYPE` (mypy), the CI-facing targets run
ruff with `--group lint` only, giving fast-fail feedback before mypy
triggers the full environment sync.

For packages where source code only conditionally imports heavy deps
(text-splitters, huggingface), `lint_package` also overrides
`UV_RUN_TYPE` to `--group lint --group typing`, skipping the ~3.5GB
`test_integration` download entirely. `lint_tests` keeps `--all-groups`
since test code legitimately imports those deps.

Additionally, `lint_imports.sh` was inconsistently wired — most packages
had the script but weren't calling it.

## Changes

**Makefile optimization**
- Introduce `UV_RUN_LINT` and `UV_RUN_TYPE` Make variables, both
defaulting to `uv run --all-groups`. For `lint_package` and
`lint_tests`, `UV_RUN_LINT` is overridden to `uv run --group lint` so
ruff runs instantly without syncing heavy deps
- For `text-splitters` and `huggingface`, override `UV_RUN_TYPE` on
`lint_package` to `uv run --group lint --group typing` — mypy runs
without downloading torch, CUDA, spacy, etc.

**mypy config for lean groups**
- Add `transformers` and `transformers.*` to `ignore_missing_imports` in
`text-splitters` pyproject.toml (conditional `try/except` import, same
treatment as existing `konlpy`/`nltk` entries)
- Add `torch`, `torch.*`, `langchain_community`, `langchain_community.*`
to `ignore_missing_imports` in `huggingface` pyproject.toml
- Add dual `# type: ignore[unreachable, unused-ignore]` in
`text-splitters/base.py` to handle the `PreTrainedTokenizerBase`
isinstance check that behaves differently depending on whether
transformers is installed

**lint_imports.sh consistency**
- Add `./scripts/lint_imports.sh` to the lint recipe in every package
that wasn't calling it (standard-tests, model-profiles, all 15
partners), and create the script for the two packages missing it
entirely (`model-profiles`, `openrouter`)
- Update all `lint_imports.sh` scripts to allow `from langchain.agents`
and `from langchain.tools` imports (legitimate v1 middleware
dependencies used by `langchain-anthropic` and `langchain-openai`)

.github/workflows/pr_labeler.yml

@@ -23,7 +23,7 @@
 # The GitHub App token is required to check private organization membership
 # and to propagate label events to downstream workflows.
 
-name: "PR Labeler"
+name: "🏷️ PR Labeler"
 
 on:
   # Safe since we're not checking out or running the PR's code.

.github/workflows/pr_labeler_backfill.yml

@@ -4,7 +4,7 @@
 # (size, file, title, contributor classification) to existing open PRs.
 # Reuses shared logic from .github/scripts/pr-labeler.js.
 
-name: "PR Labeler Backfill"
+name: "🏷️ PR Labeler Backfill"
 
 on:
   workflow_dispatch: