feat(agents): improve skill/MCP agent steering for automatic project discovery #1477

Follow-up to #1147 / #1476.

Context

The fix in #1476 removes unnecessary discovery calls when a DSN already encodes org/project identity. However, the original intent was about agent steering:

When the Sentry CLI is used via an AI agent (MCP server, custom skill, etc.), the agent does not know that sentry CLI can perform automatic project discovery from the local environment/DSN. Instead, agents currently:

• call sentry organizations list
• then sentry projects list for each org
• then try to match the local checkout to one of those projects manually

This is inefficient and error-prone.

Goal

Make it easy for agent frameworks to discover the correct Sentry target without having to re-implement the CLI's own discovery logic.

Proposed work

• Document (or expose via a machine-readable command) the recommended way for agents to obtain the resolved org/project for the current working directory.
• Consider a dedicated subcommand such as sentry resolve-target (or similar) that outputs JSON with the resolved { org, project, ... } (respecting DSN, config, env, git remote, etc.) and never performs unnecessary network calls when identity is already known.
• Ensure the output is stable and easy for agents to consume.

Happy to iterate on the exact surface area once we have a design sketch.