[Gap-Audit] Stability: group-service stubs throw generic Error, unmount React tree

[TortoiseWolfe]

Summary

src/services/messaging/group-service.ts:337-408 has 8 stub methods (the unimplemented work backing feature 011 and 043) that all throw generic Error('Not implemented'). Callers in the group UI catch GroupError | MembershipError, so the generic Error is uncaught — it bubbles up through the React render and unmounts the component tree.

Stub methods

• addMembers — line 338
• getMembers — line 348
• removeMember — line 357
• leaveGroup — line 366
• transferOwnership — line 375
• upgradeToGroup — line 384
• renameGroup — line 394
• deleteGroup — line 403

Fix

Replace each stub with throw new GroupError('Not implemented: <method>') (or MembershipError for member-ops) so existing error-boundary logic catches them as expected and surfaces a non-fatal error UI.

This is a separate concern from actually implementing the methods (which remains the larger 043 work) — it just makes the stubs fail gracefully instead of catastrophically.

Why this matters

Currently any group UI interaction with member management produces a white screen / component-tree unmount instead of a graceful error.

Related

• Code review finding: CR-027
• Feature: 043-group-service (broader implementation work)

[TortoiseWolfe]

Fixed in 53c0e4a (batch 1 stability sweep). Verified: type-check + lint + 3088 tests pass.