Add static_list completion providers to example prompt argument configs and cover them with tests

Problem/Motivation

The example prompt configurations shipped by mcp_server_examples define arguments whose valid values are described in prose (e.g. skill_level: beginner/intermediate/advanced, court_surface: hard/clay/grass). However, most of these arguments do not yet expose completion_providers, so MCP clients cannot autocomplete the valid values. This makes the examples less useful for demonstrating the MCP Server argument completion feature.

Proposed resolution

Add static_list completion providers to every example prompt argument that has a known, closed set of valid values. Also add a functional test method, assertPromptArgumentCompletions(), that calls the completion/complete MCP endpoint for each configured argument and verifies the returned values match the static lists.

Remaining tasks

• Add static_list completions to comprehensive_lesson.lesson_focus.
• Add static_list completions to match_strategy.opponent_type and match_strategy.court_surface.
• Add missing values to multi_provider_prompt.opponent_type static list.
• Add static_list completions to tennis_resources.topic.
• Add static_list completions to tennis_tip_basic.skill_level and tennis_tip_basic.focus_area.
• Add static_list completions to test_with_args.skill_level and test_with_args.surface.
• Add functional test coverage in McpServerExamplesFunctionalTest.

User interface changes

None.

API changes

None.

Data model changes

None. The mcp_server.mcp_prompt_config.* config schema already supports completion_providers.

Testing instructions

1. Install the module and run the functional test:
   

   vendor/bin/phpunit web/modules/contrib/mcp_server_examples/tests/src/Functional/McpServerExamplesFunctionalTest.php

2. Alternatively, query the MCP completion/complete endpoint for each example prompt argument and confirm the returned values match the configured static lists.