fix(ci): resolve langbot-plugin from PyPI and clear lint failures

CI on feat/sandbox failed across Unit Tests, Lint and Build Dev Image.
Root causes and fixes:

- pyproject.toml had a [tool.uv.sources] editable override pinning
  langbot-plugin to ../langbot-plugin-sdk. That path only exists in a
  paired local checkout, so `uv sync` failed on every CI runner
  ("Distribution not found"). Remove the override and regenerate uv.lock
  so langbot-plugin==0.4.0b1 resolves from PyPI, matching master.

- tests/integration/api/test_pipelines.py: the pipeline extensions
  endpoint now calls ap.skill_service.list_skills(); add the missing
  skill_service mock to the fake_pipeline_app fixture (the test came
  from master, the endpoint change from feat/sandbox).

- Apply ruff format to three src files and prettier to three web files
  that had committed formatting drift, failing `ruff format --check`
  and `pnpm lint`.

pyproject.toml

@@ -130,9 +130,6 @@ dev = [
     "ruff>=0.11.9",
 ]
 
-[tool.uv.sources]
-langbot-plugin = { path = "../langbot-plugin-sdk", editable = true }
-
 [tool.ruff]
 # Exclude a variety of commonly ignored directories.
 exclude = [