refactor(ecc): soundness fix of wiring ecc evaluations to gkr-circuit

[hero78119]

Also related to #1294
A follow-up soundness PR after rotation-flow refactor, focused on ECC->GKR bridge wiring and selector semantics.

What changed (high level)

This PR hardens ECC bridge integration with GKR by making point-binding semantics explicit and consistent across:

• CPU prover path
• GPU prover path
• native verifier path
• recursion verifier path

It also tightens selector invariants in ShardRamCircuit and layer construction.

---

Proving-flow diagram (current)

create_chip_proof
  |
  +--> [optional] prove ECC quark
  |         - input: ec_point_exprs / ec_slope_exprs witnesses
  |         - output: ecc_proof { rt, evals, sum }
  |
  +--> build main witness (records / layers)
  |
  +--> prove tower relation
  |         - build tower witnesses (r/w/logup)
  |         - sumcheck tower
  |         - output: rt_tower, tower_proof, out_evals
  |
  +--> [optional] prove rotation
  |         - output: rotation_proof + rotation points
  |
  +--> prove main constraints (GKR)
  |         - initialize out_evals at rt_tower
  |         - wire rotation claims -> selector groups
  |         - wire ECC bridge claims (x/y/s) -> selector groups
  |         - run GKR prove
  |         - output: gkr_iop_proof + opening evals + input_opening_point
  |
  +--> PCS opening
  |
  '--> assemble ZKVMChipProof

### Next
- refactor `prove ECC quark` after `proving tower relation` which make thing much clear

[kunxian-xia]

I plan to merge this first and then review them in #1299.