Fix #788: pin httpx<0.28.0 globally to fix Explorer test suite TestClient breakage (#789)

* Fix #788: pin httpx<0.28.0 globally to fix TestClient breakage

Adds an explicit httpx<0.28.0 constraint to [project.dependencies] so it
applies globally across all environments, not just dev. Without this,
different environments could resolve an incompatible transitive httpx
version and hit the same Starlette TestClient breakage independently.

Verified via git stash comparison: the unmodified baseline fails to even
collect the test suite (TestClient TypeError during collection), so this
pin doesn't just fix tests, it's what allows the full suite to run at all.

Closes #788

* Add CHANGELOG entry for #788 httpx pin fix

Documents the httpx<0.28.0 global pin from this PR under Unreleased/Fixed.

---------

Co-authored-by: KaifAhmad1 <kaifahmad087@gmail.com>

CHANGELOG.md

@@ -11,6 +11,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- **`tests/explorer/test_explorer_api.py` failed with `TypeError: Client.__init__() got an unexpected keyword argument 'app'` on current httpx** (#788, #789) by @Sameer6305
+  - `httpx>=0.28.0` removed the `app=` kwarg that Starlette's `TestClient` relies on to wrap a FastAPI app for testing; `httpx` wasn't pinned anywhere in `pyproject.toml`, so different environments could independently resolve an incompatible transitive version and hit the same break
+  - Added an explicit `httpx<0.28.0` constraint to the main `[project.dependencies]` array (not just a dev extra), so it applies globally across production, dev, and CI installs
+  - Without the pin, the full test suite fails to even complete collection (fails immediately on `tests/explorer/test_vocabulary.py` with the same `TestClient` error); with it, `tests/explorer/test_explorer_api.py` goes from 7 failed/12 passed/58 errors to 77 passed, 0 errors
+
 - **Explorer backend routes returned HTTP 200 with error/empty bodies on failure, defeating frontend error handling** (#770, #787) by @Sameer6305 and @KaifAhmad1
   - `GET /api/temporal/patterns` now raises `HTTPException(500)` on a genuine computation failure instead of silently returning an empty-but-valid `TemporalPatternResponse`; the `ImportError` fallback (optional `kg` extra not installed) is unchanged and still degrades gracefully to an empty list
   - `POST /api/ontology/create` now raises `HTTPException(500)` when ontology generation fails in either the `sample_data` or `schema_text` mode, instead of silently falling back to a partial/minimal ontology with a misleading `nodes_added` count

pyproject.toml

@@ -85,7 +85,8 @@ dependencies = [
   "python-dotenv>=1.2.1",
   "loguru>=0.7.3",
   "structlog>=22.1.0",
-  "gensim>=4.4.0"
+  "gensim>=4.4.0",
+  "httpx<0.28.0"
 ]
 
 [project.urls]