fix(agents): replace deprecated tool names with official namespaced equivalents 🤖🤖🤖 (#1382)

Update tools lists in tdd-red, tdd-green, tdd-refactor, and github-actions-expert
agents to use the current VS Code Copilot built-in tool names.

Old names were silently ignored by VS Code (documented behaviour: 'If a given
tool is not available when using the custom agent, it is ignored.').

Tool name mapping applied:
- github          → github/*
- findTestFiles   → search/fileSearch
- runTests        → execute/runTests
- runCommands     → execute/runInTerminal
- terminalCommand → execute/runInTerminal
- codebase        → search/codebase
- filesystem      → read/readFile
- problems        → read/problems
- testFailure     → execute/testFailure
- terminalLastCommand → read/terminalLastCommand
- githubRepo      → github/*

Also added missing tools present in the current VS Code tool reference:
- execute/getTerminalOutput
- read/terminalSelection

Additionally, generalised C#-specific content in TDD agents to be polyglot,
covering JavaScript/TypeScript (Jest/Vitest), Python (pytest), Java/Kotlin
(JUnit 5), and C# (.NET) — making the agents useful to the broader community.

Reference: https://code.visualstudio.com/docs/copilot/reference/copilot-vscode-features#_chat-tools

Co-authored-by: Ming <oncwnuAUeYAFR4UGlq8BEJq8Jy-k@git.weixin.qq.com>

agents/github-actions-expert.agent.md

@@ -1,7 +1,7 @@
 ---
 name: 'GitHub Actions Expert'
 description: 'GitHub Actions specialist focused on secure CI/CD workflows, action pinning, OIDC authentication, permissions least privilege, and supply-chain security'
-tools: ['codebase', 'edit/editFiles', 'terminalCommand', 'search', 'githubRepo']
+tools: ['github/*', 'search/codebase', 'edit/editFiles', 'execute/runInTerminal', 'read/readFile', 'search/fileSearch']
 ---
 
 # GitHub Actions Expert