[Epic 2] Display registry & identity

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Epic: Display registry & identity

The single source of observed truth, with stable identity that survives reconnects, ports, and identical monitors.

Milestone: M1 · PRD: REG-001…REG-012, §10.5

Scope

• DisplayRegistry actor: normalize OS events, maintain active/offline records, topology generations (REG-001/002/009).
• Persistent fingerprints + IdentityResolver confidence scoring; handle identical monitors and explicit pairing (REG-003/004/005). (scorer logic already in DisplayDomain/Identity.swift)
• Remember offline devices; aliases & tags; deterministic selector resolution (REG-006/007/010).
• Per-route capability resolution (CapabilityResolver) with explicit reasons (REG-008).
• Versioned, migratable display records with atomic writes + backup (REG-011); redacted registry diagnostics (REG-012).

Acceptance

• Identity stable across 10 reconnect cycles; ambiguous selectors never silently choose a destructive target; every unavailable capability carries a reason.