Add arch plugin (architecture + modernization skills)

.github/plugin/marketplace.json

@@ -87,6 +87,12 @@
       "description": "Play five retro Phaser mini-games in a Copilot canvas while agents work.",
       "version": "1.0.0"
     },
+    {
+      "name": "arch",
+      "source": "plugins/arch",
+      "description": "Architecture and modernization toolkit: produce a cited architecture document for a locally-cloned repo, and generate a phased modernization plan that auto-runs Documentation mode when needed.",
+      "version": "1.0.0"
+    },
     {
       "name": "arize-ax",
       "source": "plugins/arize-ax",

docs/README.plugins.md

@@ -29,6 +29,7 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-plugins) for guidelines on how t
 | ---- | ----------- | ----- | ---- |
 | [acreadiness-cockpit](../plugins/acreadiness-cockpit/README.md) | Drive Microsoft AgentRC from Copilot chat: assess AI readiness, generate Copilot instructions (flat or nested with applyTo globs for monorepos), and manage policies. Produces a self-contained static HTML dashboard at reports/index.html. | 4 items | agentrc, ai-readiness, copilot-instructions, readiness-report, monorepo, policy, dashboard |
 | [ai-team-orchestration](../plugins/ai-team-orchestration/README.md) | Bootstrap and run a multi-agent AI development team with named roles (Producer, Dev Team, QA). Sprint planning, brainstorm prompts with distinct agent voices, cross-chat context survival, and parallel team workflows. Based on a proven template that shipped a 30-game app in 5 days with zero human-written code. | 4 items | ai-team, multi-agent, sprint-planning, brainstorm, project-management, orchestration, developer-workflow |
+| [arch](../plugins/arch/README.md) | Architecture and modernization toolkit: produce a cited architecture document for a locally-cloned repo, and generate a phased modernization plan that auto-runs Documentation mode when needed. | 1 items | architecture, modernization, documentation, migration, onboarding |
 | [arize-ax](../plugins/arize-ax/README.md) | Arize AX platform skills for LLM observability, evaluation, and optimization. Includes trace export, instrumentation, datasets, experiments, evaluators, AI provider integrations, annotations, prompt optimization, and deep linking to the Arize UI. | 9 items | arize, llm, observability, tracing, evaluation, instrumentation, datasets, experiments, prompt-optimization |
 | [automate-this](../plugins/automate-this/README.md) | Record your screen doing a manual process, drop the video on your Desktop, and let Copilot CLI analyze it frame-by-frame to build working automation scripts. Supports narrated recordings with audio transcription. | 1 items | automation, screen-recording, workflow, video-analysis, process-automation, scripting, productivity, copilot-cli |
 | [awesome-copilot](../plugins/awesome-copilot/README.md) | Meta prompts that help you discover and generate curated GitHub Copilot agents, instructions, prompts, and skills. | 4 items | github-copilot, discovery, meta, prompt-engineering, agents |

docs/README.skills.md

@@ -143,6 +143,7 @@ See [CONTRIBUTING.md](../CONTRIBUTING.md#adding-skills) for guidelines on how to
 | [dependabot](../skills/dependabot/SKILL.md)<br />`gh skills install github/awesome-copilot dependabot` | Comprehensive guide for configuring and managing GitHub Dependabot. Use this skill when users ask about creating or optimizing dependabot.yml files, managing Dependabot pull requests, configuring dependency update strategies, setting up grouped updates, monorepo patterns, multi-ecosystem groups, security update configuration, auto-triage rules, or any GitHub Advanced Security (GHAS) supply chain security topic related to Dependabot. For pre-commit dependency vulnerability scanning in AI coding agents via the GitHub MCP Server, this skill references the Advanced Security plugin (`advanced-security@copilot-plugins`). Use this skill when an agent needs to scan dependencies for known vulnerabilities before committing. | `references/dependabot-yml-reference.md`<br />`references/example-configs.md`<br />`references/pr-commands.md` |
 | [devops-rollout-plan](../skills/devops-rollout-plan/SKILL.md)<br />`gh skills install github/awesome-copilot devops-rollout-plan` | Generate comprehensive rollout plans with preflight checks, step-by-step deployment, verification signals, rollback procedures, and communication plans for infrastructure and application changes | None |
 | [diagnose](../skills/diagnose/SKILL.md)<br />`gh skills install github/awesome-copilot diagnose` | Perform a systematic diagnostic scan of an AI workflow across 5 quality dimensions — prompt quality, context efficiency, tool health, architecture fitness, and safety — producing a scored report with prioritized remediation actions. | None |
+| [doc-and-modernize](../skills/doc-and-modernize/SKILL.md)<br />`gh skills install github/awesome-copilot doc-and-modernize` | Two related workflows for a locally-cloned codebase, in one skill. Documentation mode produces a single, comprehensive, verifiable architecture document primarily by reading files on disk (local-first) — use it whenever the user wants to understand, map, document, research, or onboard onto a codebase ("research this repo", "write up the architecture", "do an architecture deep dive", "document how this codebase works", "map the system design", "create an onboarding doc"). Modernization mode generates a phased plan to modernize, migrate, upgrade, or rewrite a legacy system ("modernize this", "plan the migration", "how would we rewrite this", "how do we get off this legacy stack"); if no architecture document exists yet it first runs Documentation mode, then continues straight through to the plan. It assumes the legacy stack may be dead, runs a time-boxed feasibility spike, and picks the highest achievable rung on a safety ladder instead of demanding a fully-green legacy CI gate up front. | `references/copilot-instructions.template.md`<br />`references/migration-hazards.md` |
 | [documentation-writer](../skills/documentation-writer/SKILL.md)<br />`gh skills install github/awesome-copilot documentation-writer` | Diátaxis Documentation Expert. An expert technical writer specializing in creating high-quality software documentation, guided by the principles and structure of the Diátaxis technical documentation authoring framework. | None |
 | [dotnet-best-practices](../skills/dotnet-best-practices/SKILL.md)<br />`gh skills install github/awesome-copilot dotnet-best-practices` | Ensure .NET/C# code meets best practices for the solution/project. | None |
 | [dotnet-design-pattern-review](../skills/dotnet-design-pattern-review/SKILL.md)<br />`gh skills install github/awesome-copilot dotnet-design-pattern-review` | Review the C#/.NET code for design pattern implementation and suggest improvements. | None |

plugins/arch/.github/plugin/plugin.json

@@ -0,0 +1,20 @@
+{
+  "name": "arch",
+  "description": "Architecture and modernization toolkit: produce a cited architecture document for a locally-cloned repo, and generate a phased modernization plan that auto-runs Documentation mode when needed.",
+  "version": "1.0.0",
+  "keywords": [
+    "architecture",
+    "modernization",
+    "documentation",
+    "migration",
+    "onboarding"
+  ],
+  "author": {
+    "name": "Awesome Copilot Community"
+  },
+  "repository": "https://github.com/github/awesome-copilot",
+  "license": "MIT",
+  "skills": [
+    "./skills/doc-and-modernize/"
+  ]
+}

plugins/arch/README.md

@@ -0,0 +1,25 @@
+# Arch Plugin
+
+Architecture and modernization toolkit for locally-cloned repositories. It produces a single, cited architecture document from the code on disk, and generates a phased modernization plan that automatically runs Documentation mode first when no architecture document exists yet.
+
+## Installation
+
+```bash
+copilot plugin install arch@awesome-copilot
+```
+
+## What's Included
+
+### Skills
+
+- **`doc-and-modernize`** — Two complementary workflows for a locally-cloned repository, in one skill (installed via this plugin it surfaces as `arch:doc-and-modernize`):
+  - **Documentation mode** — Produce one comprehensive, verifiable architecture document for a repository you already have checked out locally. Works local-first (prefers the local checkout, treating remote/API lookups as a flagged last resort), cites every claim to a file + line, flags unverified facts, resolves contradictions, and deep-dives the most complex subsystems. Ideal for onboarding docs and system-design maps.
+  - **Modernization mode** — Generate a phased modernization plan for a legacy codebase. If a current architecture document exists it builds on it; otherwise it first runs the Documentation mode workflow to produce one, then continues to the plan. Produces per-feature migration docs, tech-stack recommendations with ADRs, and an adaptive, safety-laddered phased implementation plan.
+
+## Source
+
+This plugin is part of [Awesome Copilot](https://github.com/github/awesome-copilot).
+
+## License
+
+MIT