feat: modernize langchain integration social tools

[daveomri]

Third PR on feat/modernize-langchain-integration. Depends on core tools and native components. Adds seven social media Actor tools.

~545 lines of new code, ~570 lines of tests.

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New tools (_actor_tools.py)

• ApifyInstagramScraperTool
  • wraps apify/instagram-scraper; search_type: user, hashtag, post, comments; optional date filter via only_posts_newer_than
• ApifyLinkedInProfilePostsTool
  • wraps apimaestro/linkedin-profile-posts; takes a profile URL or username
• ApifyLinkedInProfileSearchTool
  • wraps harvestapi/linkedin-profile-search; free-text keyword search over profiles
• ApifyLinkedInProfileDetailTool
  • wraps apimaestro/linkedin-profile-detail; optional include_email
• ApifyTwitterScraperTool
  • wraps apidojo/twitter-scraper-lite; search_mode: search, user, replies; optional ISO date bounds
• ApifyTikTokScraperTool
  • wraps clockworks/tiktok-scraper; search_type: search, user, hashtag
• ApifyFacebookPostsScraperTool
  • wraps apify/facebook-posts-scraper; public pages only; optional date filter

All seven subclass _ApifyGenericTool: handle_tool_error=True, _clamp_timeout/_clamp_items ceilings, APIFY_API_TOKEN env fallback, sync-only _run.

ApifyToolsClient additions (_client.py)

Seven new methods

• instagram_scrape, linkedin_profile_posts, linkedin_profile_search, linkedin_profile_detail, twitter_scrape, tiktok_scrape, facebook_posts_scrape
• each mapping simplified params to the Actor's input schema and reusing run_actor_and_get_items + _list_items_or_raise.

Exports (__init__.py)

APIFY_SOCIAL_TOOLS list added alongside APIFY_CORE_TOOLS and APIFY_ACTOR_TOOLS. Bind only the group(s) you need; loading all at once bloats the LLM context.

No breaking changes. All additions are additive; existing ApifyActorsTool, ApifyDatasetLoader, and ApifyWrapper behavior is unchanged.

Tests

• test_actor_tools.py (~330 lines): happy path, param mapping, max_results clamping, RuntimeError/ValueError -> ToolException, empty results, parametrized handle_tool_error check across all seven tools
• test_client.py (~240 lines): input mapping for all seven new client methods, unsupported-mode ValueErrors

Suggested reading order: _client.py -> _actor_tools.py -> __init__.py → tests

Merge target: feat/modernize-langchain-integration, not main. Rebase after [#28](#28) and [#29](#29) land. Docs and notebooks follow in a separate PR.