feat: add Steam Workshop integration

[CodeKeanu]

Summary

Adds Steam Workshop integration with 3 new tools for discovering, searching, and exploring mods and community content.

Changes

• New endpoint module: src/steam_mcp/endpoints/steam_workshop.py
  • search_workshop_items - Search Workshop mods by game with text/tag filtering and sorting
  • get_workshop_item_details - Get detailed Workshop item info (description, subscribers, dependencies)
  • get_workshop_collection - Get items from a Workshop collection
• Unit tests: 20 tests with mocked API responses in tests/test_steam_workshop.py
• Documentation: README updated (32 → 35 tools), CHANGELOG entry added

Features

• Text search and tag filtering support
• Sort by popular, trending, recent, or rating
• JSON and text output formats via supports_json=True
• Graceful handling of games without Workshop support
• Subscriber/favorite counts, ratings, file sizes
• Dependencies and collection support

Testing

• All 235 existing tests pass
• 20 new workshop tests pass
• Code follows existing patterns in the codebase

Checklist from Issue

• New steam_workshop.py endpoint module with auto-discovery
• search_workshop_items supports text search, tag filtering, and sorting
• get_workshop_item_details returns comprehensive item information
• get_workshop_collection returns collection contents
• Graceful error for games without Workshop support
• Unit tests with mocked API responses
• Tool count updated in README (32 → 35)
• CHANGELOG entry added

Closes #5

🤖 Generated with Claude Code

[CodeKeanu]

Code Review Fixes Applied

Based on review by ml-python-mcp-expert agent, the following issues have been addressed:

Must-Fix (4 items)

• ✅ None values in tag list comprehension - Added filter to exclude tags with missing/None tag key
• ✅ Silent exception catch - Added logging for failed batch fetches instead of silent pass
• ✅ Timezone-naive datetime - Changed to use UTC timezone with explicit "UTC" suffix in output
• ✅ Added logging import - Module now imports logging and creates logger

Should-Fix (4 items)

• ✅ Input validation - Added validation for empty/whitespace workshop_id and collection_id
• ✅ Standardized JSON errors - Removed extra fields from empty search results error response
• ✅ 50-item limit documentation - Added note to get_workshop_collection description
• ✅ Negative timestamp handling - Changed ts == 0 to ts <= 0 check

New Tests Added

• test_format_timestamp_negative - Validates negative timestamps return "Unknown"
• test_empty_workshop_id_returns_error - Validates empty workshop_id validation
• test_whitespace_workshop_id_returns_error - Validates whitespace-only input
• test_empty_workshop_id_json_format - Validates JSON error response for validation
• test_empty_collection_id_returns_error - Validates empty collection_id validation
• test_whitespace_collection_id_returns_error - Validates whitespace-only input
• test_tags_with_missing_key_filtered - Validates None tag filtering

All 242 tests pass ✅

[CodeKeanu]

Type Safety Fixes Applied

Fixed the TypeError: '<' not supported between instances of 'str' and 'int' error.

Root Cause

The Steam API can return numeric fields as strings (e.g., "1000" instead of 1000). Our mock tests used proper int types, so this wasn't caught during unit testing.

Solution

Added type coercion helpers and applied them throughout:

Helper	Purpose
_safe_int(value, default=0)	Safely convert to int, handles str/None
_safe_float(value, default=0.0)	Safely convert to float, handles str/None

Fields Updated

• subscriptions, favorited, views, file_size
• vote_data.score, votes_up, votes_down
• result, file_type (for comparisons)
• time_created, time_updated
• _format_file_size() and _format_timestamp() now accept string inputs

New Tests Added (7 tests)

• test_search_handles_string_numeric_values - API returns strings for numeric fields
• test_item_details_handles_string_values - Details endpoint with string values
• test_collection_handles_string_values - Collection endpoint with string values
• test_safe_int_function - Unit test for _safe_int
• test_safe_float_function - Unit test for _safe_float
• test_format_file_size_string_input - String input handling
• test_format_timestamp_string_input - String input handling

All 249 tests pass ✅

[CodeKeanu]

It is able to sort through individual workshop items correctly and all the user to filter however they want. However, the collections feature is flawed, the user currently needs to know the id of the collection in question, there is no way for the user to be able to just get the top 5 most popular collections. The collection endpoint needs to have sorting and filtering similar to that of the "search workshop items" tool. In its current state, its not very user-friendly