Simplify telemetry hook client detection with explicit caller arguments

## Problem

The shared `track-telemetry.sh` and `track-telemetry.ps1` scripts infer the active client from hook payload fields and environment variables. Session-start payloads can omit tool- and transcript-specific fields, so the Copilot/VS Code manifest currently needs an additional environment-variable marker to distinguish VS Code from Claude Code.

Client detection is spread across payload heuristics such as `COPILOT_CLI`, `cursor_version`, VS Code tool/transcript markers, and the fallback Claude format. This is difficult to reason about and can become fragile as hook payload schemas evolve.

## Proposed improvement

Allow the telemetry scripts (and the Cursor Node dispatcher) to accept an explicit argument identifying the calling hook manifest or client family. Update each client-specific hook manifest to pass a distinct value, for example:

- `copilot-hooks.json`: `copilot-vscode` or a more specific value when the runtime can distinguish the client
- `claude-hooks.json`: `claude`
- `cursor-hooks.json`: `cursor`

Use this argument as the primary client signal while retaining payload-based detection where it is still needed, such as distinguishing Copilot CLI from VS Code within their shared manifest or identifying VS Code Insiders.

## Expected outcome

- Reduce reliance on undocumented or optional payload fields.
- Remove the special-purpose `AZURE_SKILLS_HOOK_CLIENT_FAMILY` environment variable if explicit arguments cover the same need.
- Keep Bash, PowerShell, and Node dispatcher behavior consistent.
- Preserve backward compatibility for direct script invocation and older clients by falling back to the existing detection logic when no argument is supplied.
- Add cross-client tests for argument-based detection and fallback behavior.

Start with the shared track-telemetry.sh and track-telemetry.ps1 scripts, then inspect copilot-hooks.json, claude-hooks.json, cursor-hooks.json, and the Cursor Node dispatcher. Trace the existing client-detection fallback before adding cross-client tests. Done means explicit arguments work consistently, fallback behavior remains compatible, and the special-purpose environment marker is no longer needed.

Written by the indexing model from the issue text.