Linter rule: mandatory tags/metadata on elements (e.g. teamOwner)

[miarrieta-coopenae]

Problem

In larger organizations, teams want to enforce ownership/governance metadata across the architecture model — for example, requiring every element (or every element of a given kind, like service) to carry a teamOwner tag. Today nothing in LikeC4 enforces this: a missing tag is silently allowed, so ownership data drifts and becomes unreliable over time.

Proposal

Add an opt-in lint rule, configurable per project in likec4.config.json, e.g.:

{
  "lint": {
    "mandatoryTags": [
      { "tag": "teamOwner", "kinds": ["service", "system"] }
    ]
  }
}

• If kinds is omitted, the tag is required on all elements.
• The referenced tag must already be declared in specification { tag teamOwner { ... } } (reusing the existing declared-tag mechanism, rather than free-form strings).
• Missing tags surface as validation diagnostics, so they show up both in the editor (via the language server) and in likec4 validate / CI, using the existing ValidationRegistry pipeline — no separate lint command needed.

Open questions

• Should this also support mandatory metadata keys (free-form key/value), not just declared tags?
• Should missing-tag violations be warnings or errors by default?
• Should rules be scope-able beyond kinds (e.g. by tag combination, by folder/namespace)?

Happy to help draft an implementation plan if this direction sounds good.