[Bug] Conversation templates and skills do not update dynamically on project lifecycle changes

Currently, when Eclipse starts with an empty workspace (or when projects are imported, opened, closed, or deleted during a session), conversation templates, including slash commands (/), custom prompts, and skills, do not update until Eclipse is completely restarted.

Root Cause

1. ChatCompletionService initializes its workspace list using LSPEclipseUtils.getWorkspaceFolders(), which holds a static startup snapshot from LSP4E and does not update when projects are imported or opened at runtime.
2. ChatCompletionService does not register an IResourceChangeListener on ResourcesPlugin.getWorkspace(), so project lifecycle events (adding, removing, opening, or closing projects) never trigger a re-fetch of templates from the language server.

(Note: There is also an upstream language server issue where conversation/templates skips global skills when workspaceFolders is empty, but the Eclipse client must also dynamically refresh its templates whenever workspace projects change).

Steps to Reproduce

1. Start Eclipse with an empty workspace (no open projects).
2. Open Copilot Chat and type / in the input box (observe the initial command list).
3. Import or open a project containing prompts (.github/prompts/) or skills (.github/skills/).
4. Type / in Copilot Chat again.

Expected behavior:
The newly imported project's prompts and skills appear in the / completion list dynamically.

Actual behavior:
The completion list remains unchanged until Eclipse is restarted.

Start in ChatCompletionService, especially its use of LSPEclipseUtils.getWorkspaceFolders(), then inspect how ResourcesPlugin exposes project lifecycle events. Reproduce with an empty workspace and import or open a project containing .github/prompts/ or .github/skills/. Done means the slash-command list refreshes without restarting Eclipse.