feat: Skill/package discovery from APM and automated update checking

Problem

AgentRC generates repo-specific instructions and skills. APM distributes reusable agent packages. But there's no discovery layer connecting the two: a user running agentrc init on a TypeScript repo has no way to know that a curated typescript-conventions instruction package exists on APM, and installed packages have no mechanism to receive updates when upstream content improves.

This gap means:

• Teams duplicate effort creating instructions that already exist as shared packages
• Installed packages go stale as best practices evolve
• There's no feedback loop from AgentRC's analysis to APM's package ecosystem

Proposal

1. Skill/package discovery during init and instructions

When agentrc init or agentrc instructions runs, and APM is available:

agentrc init

Analyzing repository...
  Language: TypeScript (98%), Framework: React, Test: Vitest

📦 Recommended APM packages for this repo:
  microsoft/typescript-conventions    — TypeScript coding standards & patterns
  microsoft/react-best-practices      — React component & hook guidelines
  microsoft/vitest-testing            — Vitest testing patterns

Install recommended packages? [y/N]

Implementation:

• After agentrc analyze, map detected languages/frameworks/tools to APM package tags
• Query APM registry (or a curated mapping file) for matching packages
• Present recommendations with descriptions
• If user accepts, delegate to apm install <package>

2. Update checking

Add an agentrc update command (or integrate into agentrc readiness):

agentrc update --check

Installed APM packages:
  microsoft/typescript-conventions  v1.2.0 → v1.3.0 (update available)
  microsoft/react-best-practices   v2.0.1 (up to date)

Run `apm update` to update all packages.

This reads the local APM manifest (apm.yml / apm-lock.yml) and checks for newer versions.

3. Readiness criterion for package freshness

Add a readiness criterion under the AI tooling pillar:

Criterion ID	What it checks	Impact
apm-packages-current	All installed APM packages are on latest version	Medium
apm-recommended-installed	Recommended packages for detected stack are installed	Low

4. Curated package mapping

Maintain a mapping file (in AgentRC or shared):

{
  "typescript": ["microsoft/typescript-conventions"],
  "react": ["microsoft/react-best-practices"],
  "python": ["microsoft/python-standards"],
  "rust": ["microsoft/rust-conventions"]
}

This can start as a static file and evolve into an API or registry query.

Design considerations

• APM is optional — discovery features degrade gracefully when APM isn't installed (just skip recommendations)
• No auto-install — always prompt the user; --yes skips APM suggestions entirely (consistent with init bridge in PR #94)
• Subprocess boundary — AgentRC calls apm CLI commands, doesn't import APM's Python internals
• Registry vs. static mapping — start with a static mapping file, evolve to registry queries as the APM ecosystem grows

Context

• Discussed in "AgentRC: Quick Chat on Futures" meeting
• Question of overlap with marketplaces like "Awesome Copilot"
• Clarification: AgentRC = repo-specific generation, APM = distribution of reusable packages; discovery bridges the two
• Related: APM integration epic #96, reference APM package #99, init bridge PR #94

Start with the existing init bridge referenced by PR #94 and the APM integration context in epic #96. Trace the agentrc analyze, init, instructions, readiness, and proposed update entry points, along with the apm.yml and apm-lock.yml manifests and the proposed curated mapping file. Done means optional APM discovery, update checking, and readiness criteria work without APM and preserve the stated prompting behavior.