chore: add sentry-issue skill

[m3taphysics]

PR: Sentry Issue Investigation Skill for Claude Code

What does this PR change?

Adds a new Claude Code skill (sentry-issue) that automates Sentry issue investigation for the Unity Explorer project.

Previously, investigating a Sentry crash required manually fetching the issue from the Sentry UI, cross-referencing stack frames with local source files, and reasoning about the cause from scratch each time. This skill encodes that workflow so it can be triggered just by pasting a Sentry short ID (e.g. UNITY-EXPLORER-NH5) or a raw exception callstack into Claude Code.

The skill:

• Fetches the full issue + latest event stacktrace from the Sentry API
• Filters frames to project-owned code and maps them to local source files
• Reads the crash site and surrounding context
• Matches the crash against known patterns in this codebase (async/UniTask lifetime, ECS ref invalidation, CTS not cancelled on dispose, pool object reuse, AssetPromise misuse, etc.)
• Produces a structured report: issue overview, reproduction steps, ranked root cause candidates with source evidence, and concrete fix suggestions
• Offers to create a fix branch off dev and reminds the developer to include the issue ID in the commit message for automatic Sentry resolution on deploy

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Test Instructions

Prerequisites

• Claude Code CLI installed and authenticated
• A .env file in the repo root containing SENTRY_AUTH_TOKEN=<token> with issue:read scope
  (Get a token from https://decentraland.sentry.io/settings/account/api/auth-tokens/)

Test Steps

1. Open a terminal in the repo root and launch Claude Code
2. Paste a known Sentry short ID, e.g.:

   check sentry issue UNITY-EXPLORER-NH5
   

3. Claude should fetch the issue, locate the relevant source files, and produce a structured report with root cause candidates and suggested fixes
4. At the end of the report, Claude should offer to create a fix branch — confirm and verify fix/sentry-UNITY-EXPLORER-NH5 is created off dev
5. Alternatively, paste a raw exception callstack (no Sentry ID) — the skill should skip the API fetch and proceed directly to source file lookup and analysis

Additional Testing Notes

• If SENTRY_AUTH_TOKEN is missing or empty, Claude should surface a clear setup message rather than failing silently
• Test with an issue ID that doesn't exist — Claude should report it wasn't found and ask the user to verify
• The skill is non-invasive: it only reads files and makes read-only Sentry API calls — no code is modified unless the user explicitly proceeds to a fix

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Quality Checklist

• Changes have been tested locally
• Documentation has been updated — skill description is self-documenting via SKILL.md
• Performance impact has been considered — read-only, no impact on runtime
• For SDK features: N/A

[github-actions]

Build failed! Check the logs to see what went wrong

[pravusjif]

LGTM