Tsuga skills consolidation with documentation

[gus-tsuga]

Problem

The plugin surface had two installable plugins, tsuga and telemetry, with duplicated or stale skill references across packaging docs, runtime skills, and setup prompts.

That made install behavior harder to reason about and left users with split guidance for Tsuga workflows, OpenTelemetry instrumentation, telemetry debugging, and audits.

The skills also carried too much standalone reference content. That content can drift from the Tsuga documentation, which should be the single source of truth for product behavior, CLI syntax, and supported workflows.

New State

This PR consolidates everything into one tsuga plugin under plugins/tsuga/skills/.

The consolidated skills are now anchored to Tsuga documentation as the source of truth. Skills focus on routing, workflow shape, safety rules, and when to consult the docs, instead of duplicating long-lived product reference material that can go stale.

The new plugin contains:

• Tsuga CLI reference and live investigation workflows.
• Dashboard, monitor coverage, incident, and service-health skills.
• Consolidated OpenTelemetry guidance via otel-instrumentation, otel-collector, and signal-choice-advisor.
• Consolidated telemetry debug/audit workflows via tsuga-debug-telemetry-ingestion and tsuga-audit-telemetry-quality.
• Updated docs and prompts using ${CLAUDE_PLUGIN_ROOT} paths instead of stale setup-skills references.
• Final manifest version 0.8.0 in both marketplace and plugin manifests.

Review Guide

1. refactor(plugin): collapse distribution to tsuga
2. refactor(otel): consolidate OpenTelemetry guidance
3. feat(tsuga): add consolidated telemetry debug and audit skills
4. chore(tsuga): tighten CLI safety and investigation guidance
5. docs(skills): fix consolidated skill references
6. release: bump tsuga plugin to 0.8.0