[ctfbruce]

Groups can now organize shared experiments and results without sharing account credentials. Adds communities with one-use invitations, projects, optional experiment collections, immutable saved revisions, compiled-bundle validation and read-only access to explicitly shared measurements.

Members can submit measurements against an owner-funded community budget. USDC deposits use the existing signed payment flow; TEST sponsorship uses the creator's existing allowance. Reservations, membership, settlement and project history are checked atomically, while the actual submitting account remains the run owner. Community-funded measurements stay in their funding project's history. The executor measurement engine and protocol are unchanged.

Requires dispatcher migrations 32 and 33 and exposes API 1.23. Deploy console !20 after upgrading the dispatcher.

Validation:

• Complete API, payments, database and storage-check package tests and vet pass.
• Focused race tests cover invitations, sharing, revisions, concurrent reservations, network changes, settlement and quota cleanup.
• All 22 new API operations exercise recorded HTTP exchanges at both root and /api.
• An owned dispatcher/executor rehearsal passes real HTTP execution, creator-funded member runs, isolation, restart persistence and revoked-member access/spending.

Limits: community members can spend the entire funded balance; no per-member limits or unused-deposit withdrawal interface. USDC behavior is covered by receipt/chain fixtures; an actual community browser-wallet deposit has not yet been rehearsed. TEST sponsorship has been exercised end to end.

Closes #445.