#4239 swamp issue: file bugs, features and security reports against the platform source

Problem

swamp-club now has a platform issue source (swamp-club PR #1466), so bugs, features and security reports can be raised against the platform. The CLI has no way to file one.

The API already accepts it: POST /api/v1/lab/issues takes source: "platform" from any signed-in operative.

Proposed solution

Let swamp issue bug, swamp issue feature and swamp issue security file an issue with the platform source, for any logged-in user rather than only admins.

• The exact flag spelling is open.
• Without it, the commands keep filing with the source they use today.
• It cannot be combined with --extension, which routes a report elsewhere.

Behaviour to keep

• Visibility follows the type: Platform bugs and features are public, and security reports stay restricted to admins and the author.
• This adds no way to file the admin-only platform type, which the Lab now labels Internal. The platform source and the platform type are separate fields that share a name, so help text and docs should keep them distinct.
• The classifier does not rewrite the platform source, so an explicit choice sticks.

Out of scope

swamp issue search --source platform already passes through as a filter, and --type platform keeps its current meaning.

Docs

Update the swamp issue manual page and the issue guide in the swamp skill.