docs(issue): add command reference for explain and plan

[betegon]

Summary

Adds detailed command reference documentation for sentry issue explain and sentry issue plan to the issue commands page. These commands were documented in features.md at a high level but lacked the detailed syntax, options, and examples that list and view have.

Changes

Added documentation for both commands following the existing format:

• Arguments and options tables
• Multiple usage examples (numeric ID, short ID, short suffix)
• Requirements section noting Seer/GitHub prerequisites

Test plan

• Preview the docs locally to verify markdown renders correctly
• Check that the format matches existing list and view sections

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Closes #136

[github-actions]

Semver Impact of This PR

🟢 Patch (bug fixes)

📋 Changelog Preview

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New Features ✨

• (api) Add custom User-Agent header to API requests by BYK in #125
• (docs) Add Sentry SDK for error tracking, replay, and metrics by betegon in #122
• (project) Improve project list and view output by betegon in #129
• (telemetry) Improve Sentry instrumentation by BYK in #127

Bug Fixes 🐛

• (npx) Suppress Node.js warnings in npm package by BYK in #115

Documentation 📚

• (issue) Add command reference for explain and plan by betegon in #137

• (skill) Add well-known skills discovery endpoint by sergical in #135

Internal Changes 🔧

• Allow PRs to merge when CI jobs are skipped by BYK in #123

Other

• fix links to commands from /getting-started by souredoutlook in #133

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_{🤖 This preview updates automatically when you update the PR.}

[github-actions]

PR Preview Action v1.8.1
🚀 View preview at https://cli.sentry.dev/pr-preview/pr-137/
Built to branch gh-pages at 2026-01-30 23:17 UTC. Preview will be ready when the GitHub Pages deployment is complete.

[github-actions]

Codecov Results 📊

✅ Patch coverage is 100.00%. Project has 1760 uncovered lines.
✅ Project coverage is 67.66%. Comparing base (base) to head (head).

Files with missing lines (24)

File	Patch %	Lines
human.ts	30.90%	⚠️ 682 Missing
resolve-target.ts	18.93%	⚠️ 257 Missing
oauth.ts	25.39%	⚠️ 191 Missing
resolver.ts	3.23%	⚠️ 120 Missing
api-client.ts	67.61%	⚠️ 103 Missing
errors.ts	5.94%	⚠️ 95 Missing
migration.ts	47.44%	⚠️ 82 Missing
api.ts	89.80%	⚠️ 47 Missing
seer.ts	75.54%	⚠️ 45 Missing
errors.ts	73.17%	⚠️ 33 Missing
seer.ts	76.15%	⚠️ 31 Missing
preload.ts	39.02%	⚠️ 25 Missing
detector.ts	87.79%	⚠️ 16 Missing
auth.ts	94.21%	⚠️ 7 Missing
index.ts	95.06%	⚠️ 4 Missing
colors.ts	91.84%	⚠️ 4 Missing
telemetry.ts	97.28%	⚠️ 4 Missing
schema.ts	88.00%	⚠️ 3 Missing
env-file.ts	97.17%	⚠️ 3 Missing
utils.ts	98.64%	⚠️ 2 Missing
alias.ts	98.56%	⚠️ 2 Missing
project-aliases.ts	97.40%	⚠️ 2 Missing
java.ts	97.22%	⚠️ 1 Missing
parser.ts	98.63%	⚠️ 1 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    67.66%    67.66%        —%
==========================================
  Files           47        47         —
  Lines         5442      5442         —
  Branches         0         0         —
==========================================
+ Hits          3682      3682         —
- Misses        1760      1760         —
- Partials         0         0         —

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