fix(agents): remove invalid tool names across multiple agents 🤖🤖🤖 (#1384)

Remove or replace tool names that VS Code Copilot silently ignores
because they do not exist in the current built-in tools reference.

Files changed:
- context-architect: 'codebase', 'terminalCommand' → proper namespaced tools
- debug: 'web/githubRepo', bare 'search' → remove/replace
- implementation-plan: 'think', 'search/changes', 'findTestFiles',
  'search/searchResults', 'web/githubRepo', 'execute/runNotebookCell',
  'read/getNotebookSummary', 'read/readNotebookCellOutput', bare 'search' → remove
- janitor: 'browser', 'microsoft.docs.mcp/*', 'read/getTaskOutput' →
  remove browser & mcp wildcard; move getTaskOutput to execute/ namespace
- plan: 'web/githubRepo', 'azure-mcp/search', 'search/searchResults' → remove
- principal-software-engineer: 'browser' → remove
- specification: old-style bare tool names → correct namespaced equivalents

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

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

agents/specification.agent.md

@@ -1,7 +1,7 @@
 ---
 description: 'Generate or update specification documents for new or existing functionality.'
 name: 'Specification'
-tools: ['changes', 'search/codebase', 'edit/editFiles', 'extensions', 'web/fetch', 'findTestFiles', 'githubRepo', 'new', 'openSimpleBrowser', 'problems', 'runCommands', 'runTasks', 'runTests', 'search', 'search/searchResults', 'runCommands/terminalLastCommand', 'runCommands/terminalSelection', 'testFailure', 'usages', 'vscodeAPI', 'microsoft.docs.mcp', 'github']
+tools: ['search/codebase', 'search/usages', 'edit/editFiles', 'vscode/extensions', 'web/fetch', 'vscode/openSimpleBrowser', 'read/problems', 'execute/runTests', 'read/terminalLastCommand', 'read/terminalSelection', 'execute/testFailure', 'vscode/vscodeAPI']
 ---
 # Specification mode instructions