Giving teeth to expected EC disabling: P2XX(-T)(-ML)

A bitcoin-dev mailing list proposal by Pieter Wuille addressing the weakest link in "disable elliptic-curve spending later" migration plans: nothing binds the future ecosystem to actually perform the promised disabling, so it is unclear what quantum resistance such an output type really offers. He proposes codifying automatic triggers into the consensus rules that introduce a post-quantum output type (whether Taproot-shaped or P2MR-shaped):

• Tripwire (-T), crediting an idea from Tadge Dryja: pick a NUMS point — a public key constructed so that provably nobody knows its private key — and if any transaction ever validly signs with it, elliptic-curve spending in the new output type shuts off from the next block. Only a working CRQC could produce such a signature, so the tripwire is an unfakeable proof that elliptic-curve cryptography has fallen. Because any CRQC owner could fire it at will, users must treat EC disabling as possible at any time — which, Wuille argues, also makes a planned disabling soft fork non-confiscatory and pushes wallets to genuinely test their post-quantum paths.
• Miner lockdown (-ML), credited to Sjors Provoost: ship the EC-disabling soft fork bundled with the output type but with a very long activation window, letting a hashrate majority trigger it faster than the ecosystem could coordinate a new soft fork if a quantum emergency arrived.

Replies probe the edges: false-positive activations, miners' incentive to trigger disabling early for fee revenue (conduition), detection of tripwire proofs outside mined blocks, alternative activation mechanics (Anthony Towns), and whether miners colluding with a CRQC owner could counter-fork to undo a lockdown (Antoine Riard).