docs: add PLUGINS.md — plugin system overview + getting started

[shuff57]

Adds a top-level PLUGINS.md documenting Listenarr's runtime plugin system.

What it covers

• What the plugin system is: repositories are a catalog you install from selectively, not a bundle — adding a repository populates the Settings → Plugins list, and you install only what you want.
• How install / update / uninstall work (and that the app restarts to load changes).
• The plugin package layout (plugin.json + optional backend .dll + optional ui/ bundle) and that plugins own their own data without touching the core schema.
• How to run your own repository (the catalog JSON shape).
• A getting-started pointer to an example plugin catalog: https://github.com/shuff57/listenarr-plugins

Notes

• Docs only — one new file, no code changes.
• This documents the runtime plugin host (see the plugin-system work / feat(plugins): runtime-installable plugin system (loader + manager) #713). If the plugin host isn't in canary yet, this can land alongside/after it.
• The example catalog referenced is a personal/community repo; happy to adjust the wording or swap in a neutral example if you'd prefer.

🤖 Generated with Claude Code

[therobbiedavis]

@shuff57 Why not add into #713

[shuff57]

Smart, I’ll move it.

…

________________________________ From: Robbie Davis ***@***.***> Sent: Thursday, 02 July 2026 10:04:54 To: Listenarrs/Listenarr ***@***.***> Cc: shuff57 ***@***.***>; Mention ***@***.***> Subject: Re: [Listenarrs/Listenarr] docs: add PLUGINS.md — plugin system overview + getting started (PR #721) [https://avatars.githubusercontent.com/u/7907265?s=20&v=4]therobbiedavis left a comment (Listenarrs/Listenarr#721)<#721 (comment)> @shuff57<https://github.com/shuff57> Why not add into #713<#713> — Reply to this email directly, view it on GitHub<#721?email_source=notifications&email_token=AO3WMMWE2YVV7OHDTT6HQLT5C2I3NA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIOBWHA2DAMZVGQ2KM4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJLDGN5XXIZLSL5RWY2LDNM#issuecomment-4868403544>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AO3WMMXKJEZCNGZ3RNASITL5C2I3NAVCNFSNUABGKJSXA33TNF2G64TZHMYTANZQHEZTCNJZGE5US43TOVSTWNBXHE3DINZXHE3DLILWAI>. You are receiving this because you were mentioned.Message ID: ***@***.***>

[shuff57]

Folded into #713 (the plugin-system PR) — the docs belong with the feature. Closing this standalone docs PR.