explain: `os explain object` documents `ownership` as "own" | "extend" — real values are user | org | none

[os-zhuang]

packages/cli/src/commands/explain.ts:37 documents the object ownership field as:

{ name: 'ownership', type: '"own" | "extend"', description: 'Whether this object is owned or extended' }

But the real ObjectSchema.ownership field is the record-ownership model (packages/spec/src/data/object.zod.ts:632):

ownership: z.enum(['user', 'org', 'none'])   // user (default, injects owner_id) | org | none

own / extend is the package contribution kind — a distinct concept the spec explicitly calls out as separate from record-ownership (object.zod.ts:627,637). So os explain object prints the wrong allowed values and a misleading description for ownership.

Fix: update the explain entry to type: "'user' | 'org' | 'none'" with a description like "Record-ownership model: user (default, injects a reassignable owner_id) | org | none (no per-record owner)".

Found during the #1880 docs implementation-accuracy audit (PR #3243); out of scope for that docs-only PR.