test(e2e): add long-text and provider-limit tests; isolate curl configure

Add four e2e tests covering long-text behaviour and provider boundaries:
- memory_add_long_text_chunking + memory_search_long_text_sections:
  structural and retrieval coverage for multi-chunk inputs.
- memory_search_under_token_limit (~5KB, single chunk; passes) and
  memory_search_truncation_signature / _near_model_context (~10KB /
  ~19.5KB, rejected by provider): document vectors.space's 1024-token
  batch ceiling.

Also: RUN_TEST no longer prints PASSED after a test fails, and Makefile
strips LDFLAGS/CPPFLAGS/CFLAGS/LIBS from curl's ./configure so rebuilds
work in shells with Homebrew-style env exports.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: andinux

Makefile

@@ -561,7 +561,7 @@ ifeq ($(PLATFORM),windows)
 else
 	unzip -o $(CURL_ZIP) -d $(CURL_DIR)/src/.
 endif
-	cd $(CURL_SRC) && ./configure \
+	cd $(CURL_SRC) && env -u LDFLAGS -u CPPFLAGS -u CFLAGS -u LIBS ./configure \
 	--without-libpsl \
 	--disable-alt-svc \
 	--disable-ares \