feat: add native Gemini 3.8 Flash support (#7284)

* feat(llm): add Gemini 3.8 Flash support

- Register Gemini 3.8 Flash in CrewAI and CLI model catalogs
- Add 1,048,576-token context window mapping
- Add native Gemini provider support
- Add Gemini 3.8 Flash to the CLI model picker
- Add native model detection coverage for gemini/ and google/ formats
- Add context window regression coverage

Closes #7241

* test: add VCR cassette for gemini-3.8-flash

* chore: stop tracking .env.test

* Bringing back .env.test

---------

Co-authored-by: Vidit Ostwal <110953813+Vidit-Ostwal@users.noreply.github.com>
Co-authored-by: ViditOstwal <viditostwal@gmail.com>

lib/cli/src/crewai_cli/constants.py

@@ -177,6 +177,7 @@ MODELS: dict[str, list[str]] = {
         "claude-haiku-4-5-20251001",
     ],
     "gemini": [
+        "gemini/gemini-3.8-flash",
         "gemini/gemini-3-pro-preview",
         "gemini/gemini-1.5-flash",
         "gemini/gemini-1.5-pro",

lib/cli/src/crewai_cli/create_json_crew.py

@@ -75,6 +75,7 @@ _PROVIDER_MODELS: dict[str, list[tuple[str, str]]] = {
         ("claude-sonnet-4-6", "Claude Sonnet 4.6"),
     ],
     "gemini": [
+        ("gemini-3.8-flash", "Gemini 3.8 Flash"),
         ("gemini-3.5-flash", "Gemini 3.5 Flash"),
         ("gemini-3.1-pro-preview", "Gemini 3.1 Pro (preview)"),
         ("gemini-3-flash-preview", "Gemini 3 Flash (preview)"),