docs: update default model examples to gpt-5 and gemini-3.5-flash

[aheritier]

Documentation updates for recently merged features

This PR brings the /docs content in sync with changes merged into main in the last 36 hours.

Changes

Commit	Source PR	What changed
57b6f53	#2997	Update default model examples: gpt-5-mini → gpt-5, gemini-2.5-flash → gemini-3.5-flash

Details

docs/configuration/overview/index.md — Updates the DOCKER_AGENT_DEFAULT_MODEL environment variable example value from openai/gpt-5-mini to openai/gpt-5, reflecting the bumped default in PR #2997.

docs/providers/openai/index.md — Updates the primary inline and named model examples from gpt-5-mini to gpt-5. The Available Models table is left intact — gpt-5-mini remains a valid model and is correctly listed there.

docs/providers/google/index.md — Updates the primary inline and named model examples from gemini-2.5-flash to gemini-3.5-flash. The Available Models table is left intact — gemini-2.5-flash remains a valid model and is correctly listed there.

PRs reviewed but no doc changes needed

Source PR	Reason
#3000	Hooks docs (docs/configuration/hooks/index.md) were updated as part of the PR itself
#2999	Already a docs-only PR
#2996	Coder agent model rename (haiku → fast) has no doc references — only claude-haiku-4-5 (a real model name) appears in docs, not the internal config alias
#2995	Dependency bump — no user-facing changes
#2993	Self-update docs were included in the PR itself

[docker-agent]

Assessment: 🟢 APPROVE

This is a clean, low-risk documentation-only PR. The model name updates (gpt-5-mini → gpt-5, gemini-2.5-flash → gemini-3.5-flash) are applied consistently across all three affected files. No bugs, logic errors, or security issues were found in the changed lines.