[Team] Add persisted team, human and bot-owner identities #47

Planning ID: TODO-B

Proposed issue / PR title: feat(identity): persist team members and owner-bound bots.

Goal: replace implicit single-user ownership with explicit stable identities.

Scope: versioned team/member records, immutable IDs, bot owner binding and designated Chief pointer; validate uniqueness and references. Migrate a legacy installation by an explicit setup step assigning its existing bots to the initial owner. Preserve bot/session IDs and private histories. Retain legacy single-owner use after migration.

Out of scope: sign-in UI, shared room enablement and ownership-transfer UI.

Dependencies: TODO-A (#46).

Code area: core store, roster, public types and store/legacy-state tests; regenerate the appropriate upstream patch topics.

Acceptance and tests: fresh state and representative legacy state load correctly; migration is idempotent and restart-safe; malformed ownership fails closed; no display-name matching grants ownership. Back up old state before a format change, and document that older binaries must not silently overwrite the new schema.

Delivery

One focused implementation PR for this issue. This is planned work, not a claim of shipped multi-human support. Preserve the pristine upstream pin and generated patch/client boundaries. Keep team mode disabled until the documented authorization gates pass. Record exact tested head, executed checks, missing checks and independent review. No production credentials or live deployment are part of this issue.