feat(examples): add multi-chain TDIP delegation chain example

[hilarl]

examples: add multi-chain delegation example with Plonky3 cart-hash anchoring

Follow-up to #25 (which introduced protocol-landscape/tenzro-tdip.md

• examples/tenzro_tdip_flow.py covering the single-chain TDIP↔VI
  composition). This PR adds a second runnable example exercising the
  multi-chain dimension of TDIP delegation that docs(protocol-landscape): add Tenzro TDIP integration mapping + example #25 documented but did
  not demonstrate.

Motivation

TDIP's DelegationScope already lists allowed_chains as a first-
class axis alongside max_transaction_value, max_daily_spend,
allowed_operations, allowed_payment_protocols, and time_bound. Of
those six axes, allowed_chains is the most-tested in the upstream
Rust crate (crates/tenzro-identity/src/delegation.rs) but the
least-demonstrated in any portable example — partly because
single-VM agentic-commerce demos rarely surface it.

This example fills that gap. A single VI L1 + L2 + four per-purchase
L3a records drive purchases across four Tenzro VM facades:

• Ethereum via wTNZO ERC-20 pointer (0x7a4bcb...)
• Solana via wTNZO-SPL adapter
• Canton via TNZO CIP-56 holding
• Polygon not in allowed_chains — rejected with the typed
  ChainNotAllowed reason.

Each accepted purchase generates a Plonky3 STARK over a canonical cart
payload, computes the 32-byte
compute_zk_commitment(circuit_id, proof_bytes, public_inputs) =
SHA-256(circuit_id ‖ proof_bytes ‖ Σ(len_le(pi) ‖ pi)), and records
it in a mock ZkCommitmentRegistry. The VI L3a transaction_id carries
the same canonical cart hash, so the off-chain VI record and the
on-chain ZK commitment are cross-verifiable — useful for the case where
a merchant on chain X wants to confirm an authorization that settled on
chain Y.

What's in this PR

examples/tenzro_did_chain_multichain.py (new, ~520 lines)

Self-contained, mocks both TDIP and the on-chain registry. With
TENZRO_RPC_URL set (e.g. https://rpc.tenzro.network), the example
issues real tenzro_createZkProof JSON-RPC calls instead of computing
proof bytes locally. The five-ceiling check at the heart of the
example:

1. VI chain validity (verify_chain)
2. VI per-purchase constraints (check_constraints)
3. TDIP DelegationScope::enforce_operation — operation, value,
   protocol, time
4. TDIP DelegationScope.allowed_chains membership (per-VM gate)
5. TDIP runtime SpendingPolicy::check

(In the Rust source, (3) and (4) are a single enforce_operation call;
the Python mock surfaces the chain check separately to make the
denial path readable.)

pytest examples/tenzro_did_chain_multichain.py is green; the example
asserts every accepted purchase settles, asserts the denied purchase
fails specifically on ChainNotAllowed, and asserts each accepted
purchase produces a unique 32-byte commitment.

protocol-landscape/tenzro-tdip.md (extension, no new file)

Adds a single subsection — Multi-chain delegation enforcement — to
the file landed in #25. The patch is provided as a separate
tenzro-tdip.patch.md describing exactly where the new prose goes;
the maintainer can squash it into the merged file. If the maintainer
prefers the patch lifted into a separate tenzro-tdip-multichain.md
(parallel to how UCP/AP2/ACP each have their own page), I'll respin.

Files

examples/tenzro_did_chain_multichain.py     # new, ~520 lines
protocol-landscape/tenzro-tdip.md           # extended (one new subsection)

No changes to spec/. No changes to src/. No changes to existing
protocol-landscape/ pages other than the same tenzro-tdip.md
extended via this PR.

Tests

• pytest clean against this PR.
• python examples/tenzro_did_chain_multichain.py runs end-to-end and
  prints the same banner-formatted output style as autonomous_flow.py
  and tenzro_tdip_flow.py from docs(protocol-landscape): add Tenzro TDIP integration mapping + example #25.
• All four ceilings are asserted per accepted purchase; the denied
  purchase is asserted to fail specifically on the chain gate.

SDK consistency

No SDK changes are required. The example uses only the existing
verifiable_intent SDK surface (create_layer1, create_layer2_autonomous,
create_layer3_payment, verify_chain, check_constraints,
build_selective_presentation, decode_sd_jwt, resolve_disclosures,
hash_disclosure). The TDIP primitives and ZkCommitmentRegistry are
mocked locally in the example file. Pointers to the real Rust
implementations:

• crates/tenzro-identity/src/delegation.rs — DelegationScope,
  is_chain_allowed
• crates/tenzro-zk — compute_zk_commitment, ZkCommitmentRegistry
  hash construction
• crates/tenzro-vm/src/precompiles.rs — ZK_VERIFY precompile
  (O(1) HashSet lookup)

Protocol-agnostic language

The VI core spec (spec/) is unchanged. All TDIP- and chain-specific
language lives in protocol-landscape/tenzro-tdip.md and the new
example. The example deliberately uses Tenzro testnet endpoints
(rpc.tenzro.network) and marks Solana / Canton facade addresses as
placeholders; nothing is mainnet-specific.

DCO sign-off

All commits in this PR carry Signed-off-by: Hilal Agil <hilal@tenzro.com>.

AI assistance disclosure

Per the project's contribution norms: parts of the wording in this PR
description, the patch to tenzro-tdip.md, and code comments in the
example were prepared with AI assistance from Claude Code. All
technical decisions, the multi-chain mapping itself, and final wording
were reviewed and authored by the human author (Hilal Agil,
hilal@tenzro.com). The TDIP and Plonky3 reference implementations in
tenzro/tenzro-network were developed independently.

Checklist

• PR title in Conventional Commits format:
  examples: add multi-chain delegation example with Plonky3 cart-hash anchoring.
• Every commit Signed-off-by (DCO).
• No changes to spec/ (TDIP-specific content stays in
  protocol-landscape/).
• Single new example file under examples/.
• pytest clean against the change.
• Example exercised end-to-end and asserts the four-plus-chain
  ceiling pattern.
• No new SDK changes required; verifiable_intent surface is
  unchanged.
• References docs(protocol-landscape): add Tenzro TDIP integration mapping + example #25 and complements (does not duplicate) its
  single-chain example.

[hilarl]

Withdrawing.