[BLOCKED: emissions redesign] Activate alpha-spoke pairs (PR3)

[LandynDev]

BLOCKED — merge gate. Do not merge until the emissions redesign answers O3.

Activates every alpha<->spoke pair and sn7<->sn74 (one line in the LAUNCH_PAIRS generator). Stacked on #708, which ships the whole mechanism; this PR adds pairs, not mechanism.

Why it is held: each alpha becomes its own scoring family (hub_leg returns the alpha). On pair count alone, before any volume clears, sol 27% / tao 26% / sn7 24% / sn74 23% of 66 pairs — alpha takes 47% of miner emissions. Volume weighting redistributes only within a family, never across, so real volume elsewhere cannot claw it back.

Also required before merge (surfaced during implementation, not blockers for PR2):

• das hubLeg/direction maps need the family rule for alpha<->spoke directions (today they only know literal hubs).
• swap_intake.hub_bounds keys bounds by hub id; an alpha anchor reads (0, 0), so is_executable_rate is permissive on alpha<->spoke pairs (the per-backing TAO size gate still applies).
• scoring.py passes the TAO purse bounds (rao) as the hub-leg bounds of an alpha-anchored lane, where is_executable_rate / min_executable_hub_leg read them as alpha units (same decimals hide it). Resolve with the emissions redesign before this merges.
• Pair count: 70 pairs after this PR (17 spokes today), not the 66 the spec estimated.

Spec: SPEC_SUBNET_TOKENS.md §6, §9, O3.