TopologyInfo account + instructions

[ben-malbeclabs]

New PDA defining a named constrained IS-IS forwarding plane with auto-assigned admin-group bit, flex-algo number, and derived EOS color. Instructions: create, delete, clear. All fields are immutable after creation.

On create, the topology creation processor MUST also iterate all existing Interface accounts with loopback_type = Vpnv4 and allocate a FlexAlgoNodeSegment entry for the new topology on each — this ensures all devices always advertise a node-SID for every defined topology without operator action.

Milestone: RFC-18: Onchain Foundation
RFC: #3288

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Files affected:

• smartcontract/programs/doublezero-serviceability/src/state/topology_info.rs (new)
• smartcontract/programs/doublezero-serviceability/src/processors/topology/ (new)
• smartcontract/programs/doublezero-serviceability/src/authorize.rs

Size: Large

Tests:

• Borsh round-trip
• Duplicate name rejected
• Delete blocked if any link still references topology
• Clear is idempotent
• Topology creation allocates FlexAlgoNodeSegment entries on all existing Vpnv4 loopbacks
• Non-foundation key rejected on create/delete/clear

Blockers: #3343 (AdminGroupBits ResourceExtension)