Migrate a Legacy Plugin off tile.json

Problem/Feature Description

The repo acme/widgets is an older Tessl plugin still shipped in the legacy tile.json form — there is no .tessl-plugin/plugin.json yet. The maintainer wants it brought fully onto the current plugin manifest form and the repo's wording brought in line, so a reader isn't left with a half-renamed project.

The relevant current contents:

tile.json (the legacy manifest, present at the repo root) and .tileignore (a build-artifact ignore file) both exist; there is no .tessl-plugin/plugin.json.

README.md:

# acme/widgets

Widgets tile for ACME's agents. 12 steering rules covering commits, testing, and release.
Install with `tessl install acme/widgets`.

skills/release/check-publish.sh:

# Poll the registry for the published version's moderation state.
#   tessl api v1/tiles/<workspace>/<name>/versions/<version>
latest=$(tessl tile info "${workspace}/${name}" | grep "Latest Version" | awk '{print $NF}')

skills/release/registry.ts:

const tileRegistry = new Registry(workspace);
export function fetchTile(name: string) { return tileRegistry.get(name); }

CHANGELOG.md (top entry):

- Migrated the build from a hand-written tile.json to the generated manifest.

Output Specification

Capture your migration plan in a file named migration-plan.md: the commands you would run and the edits you would make to the files above to complete the migration.